Merge commit 'ea01a15a654b9e1c7b37d958f4d1911882ed7781'

[unleashed.git] / kernel / vm / seg_dev.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2018 Joyent, Inc.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

/*
 * VM - segment of a mapped device.
 *
 * This segment driver is used when mapping character special devices.
 */

#include <sys/types.h>
#include <sys/t_lock.h>
#include <sys/sysmacros.h>
#include <sys/vtrace.h>
#include <sys/systm.h>
#include <sys/vmsystm.h>
#include <sys/mman.h>
#include <sys/errno.h>
#include <sys/kmem.h>
#include <sys/cmn_err.h>
#include <sys/vnode.h>
#include <sys/proc.h>
#include <sys/conf.h>
#include <sys/debug.h>
#include <sys/ddidevmap.h>
#include <sys/ddi_implfuncs.h>
#include <sys/lgrp.h>

#include <vm/page.h>
#include <vm/hat.h>
#include <vm/as.h>
#include <vm/seg.h>
#include <vm/seg_dev.h>
#include <vm/seg_kp.h>
#include <vm/seg_kmem.h>
#include <vm/vpage.h>

#include <sys/sunddi.h>
#include <sys/esunddi.h>
#include <sys/fs/snode.h>


#if DEBUG
int segdev_debug;
#define DEBUGF(level, args) { if (segdev_debug >= (level)) cmn_err args; }
#else
#define DEBUGF(level, args)
#endif

/* Default timeout for devmap context management */
#define CTX_TIMEOUT_VALUE 0

#define HOLD_DHP_LOCK(dhp)  if (dhp->dh_flags & DEVMAP_ALLOW_REMAP) \
                        { mutex_enter(&dhp->dh_lock); }

#define RELE_DHP_LOCK(dhp) if (dhp->dh_flags & DEVMAP_ALLOW_REMAP) \
                        { mutex_exit(&dhp->dh_lock); }

#define round_down_p2(a, s)     ((a) & ~((s) - 1))
#define round_up_p2(a, s)       (((a) + (s) - 1) & ~((s) - 1))

/*
 * VA_PA_ALIGNED checks to see if both VA and PA are on pgsize boundary
 * VA_PA_PGSIZE_ALIGNED check to see if VA is aligned with PA w.r.t. pgsize
 */
#define VA_PA_ALIGNED(uvaddr, paddr, pgsize)            \
        (((uvaddr | paddr) & (pgsize - 1)) == 0)
#define VA_PA_PGSIZE_ALIGNED(uvaddr, paddr, pgsize)     \
        (((uvaddr ^ paddr) & (pgsize - 1)) == 0)

#define vpgtob(n)       ((n) * sizeof (struct vpage))   /* For brevity */

#define VTOCVP(vp)      (VTOS(vp)->s_commonvp)  /* we "know" it's an snode */

static struct devmap_ctx *devmapctx_list = NULL;
static struct devmap_softlock *devmap_slist = NULL;

/*
 * mutex, vnode and page for the page of zeros we use for the trash mappings.
 * One trash page is allocated on the first ddi_umem_setup call that uses it
 * XXX Eventually, we may want to combine this with what segnf does when all
 * hat layers implement HAT_NOFAULT.
 *
 * The trash page is used when the backing store for a userland mapping is
 * removed but the application semantics do not take kindly to a SIGBUS.
 * In that scenario, the applications pages are mapped to some dummy page
 * which returns garbage on read and writes go into a common place.
 * (Perfect for NO_FAULT semantics)
 * The device driver is responsible to communicating to the app with some
 * other mechanism that such remapping has happened and the app should take
 * corrective action.
 * We can also use an anonymous memory page as there is no requirement to
 * keep the page locked, however this complicates the fault code. RFE.
 */
static struct vnode trashvp;
static struct page *trashpp;

/* Non-pageable kernel memory is allocated from the umem_np_arena. */
static vmem_t *umem_np_arena;

/* Set the cookie to a value we know will never be a valid umem_cookie */
#define DEVMAP_DEVMEM_COOKIE    ((ddi_umem_cookie_t)0x1)

/*
 * Macros to check if type of devmap handle
 */
#define cookie_is_devmem(c)     \
        ((c) == (struct ddi_umem_cookie *)DEVMAP_DEVMEM_COOKIE)

#define cookie_is_pmem(c)       \
        ((c) == (struct ddi_umem_cookie *)DEVMAP_PMEM_COOKIE)

#define cookie_is_kpmem(c)      (!cookie_is_devmem(c) && !cookie_is_pmem(c) &&\
        ((c)->type == KMEM_PAGEABLE))

#define dhp_is_devmem(dhp)      \
        (cookie_is_devmem((struct ddi_umem_cookie *)((dhp)->dh_cookie)))

#define dhp_is_pmem(dhp)        \
        (cookie_is_pmem((struct ddi_umem_cookie *)((dhp)->dh_cookie)))

#define dhp_is_kpmem(dhp)       \
        (cookie_is_kpmem((struct ddi_umem_cookie *)((dhp)->dh_cookie)))

/*
 * Private seg op routines.
 */
static int      segdev_dup(struct seg *, struct seg *);
static int      segdev_unmap(struct seg *, caddr_t, size_t);
static void     segdev_free(struct seg *);
static faultcode_t segdev_fault(struct hat *, struct seg *, caddr_t, size_t,
                    enum fault_type, enum seg_rw);
static faultcode_t segdev_faulta(struct seg *, caddr_t);
static int      segdev_setprot(struct seg *, caddr_t, size_t, uint_t);
static int      segdev_checkprot(struct seg *, caddr_t, size_t, uint_t);
static void     segdev_badop(void);
static int      segdev_sync(struct seg *, caddr_t, size_t, int, uint_t);
static size_t   segdev_incore(struct seg *, caddr_t, size_t, char *);
static int      segdev_lockop(struct seg *, caddr_t, size_t, int, int,
                    ulong_t *, size_t);
static int      segdev_getprot(struct seg *, caddr_t, size_t, uint_t *);
static uoff_t   segdev_getoffset(struct seg *, caddr_t);
static int      segdev_gettype(struct seg *, caddr_t);
static int      segdev_getvp(struct seg *, caddr_t, struct vnode **);
static int      segdev_advise(struct seg *, caddr_t, size_t, uint_t);
static int      segdev_pagelock(struct seg *, caddr_t, size_t,
                    struct page ***, enum lock_type, enum seg_rw);
static int      segdev_getmemid(struct seg *, caddr_t, memid_t *);

/*
 * XXX  this struct is used by rootnex_map_fault to identify
 *      the segment it has been passed. So if you make it
 *      "static" you'll need to fix rootnex_map_fault.
 */
const struct seg_ops segdev_ops = {
        .dup            = segdev_dup,
        .unmap          = segdev_unmap,
        .free           = segdev_free,
        .fault          = segdev_fault,
        .faulta         = segdev_faulta,
        .setprot        = segdev_setprot,
        .checkprot      = segdev_checkprot,
        .kluster        = (int (*)())segdev_badop,
        .sync           = segdev_sync,
        .incore         = segdev_incore,
        .lockop         = segdev_lockop,
        .getprot        = segdev_getprot,
        .getoffset      = segdev_getoffset,
        .gettype        = segdev_gettype,
        .getvp          = segdev_getvp,
        .advise         = segdev_advise,
        .pagelock       = segdev_pagelock,
        .getmemid       = segdev_getmemid,
};

/*
 * Private segdev support routines
 */
static struct segdev_data *sdp_alloc(void);

static void segdev_softunlock(struct hat *, struct seg *, caddr_t,
    size_t, enum seg_rw);

static faultcode_t segdev_faultpage(struct hat *, struct seg *, caddr_t,
    struct vpage *, enum fault_type, enum seg_rw, devmap_handle_t *);

static faultcode_t segdev_faultpages(struct hat *, struct seg *, caddr_t,
    size_t, enum fault_type, enum seg_rw, devmap_handle_t *);

static struct devmap_ctx *devmap_ctxinit(dev_t, ulong_t);
static struct devmap_softlock *devmap_softlock_init(dev_t, ulong_t);
static void devmap_softlock_rele(devmap_handle_t *);
static void devmap_ctx_rele(devmap_handle_t *);

static void devmap_ctxto(void *);

static devmap_handle_t *devmap_find_handle(devmap_handle_t *dhp_head,
    caddr_t addr);

static ulong_t devmap_roundup(devmap_handle_t *dhp, ulong_t offset, size_t len,
    ulong_t *opfn, ulong_t *pagesize);

static void free_devmap_handle(devmap_handle_t *dhp);

static int devmap_handle_dup(devmap_handle_t *dhp, devmap_handle_t **new_dhp,
    struct seg *newseg);

static devmap_handle_t *devmap_handle_unmap(devmap_handle_t *dhp);

static void devmap_handle_unmap_head(devmap_handle_t *dhp, size_t len);

static void devmap_handle_unmap_tail(devmap_handle_t *dhp, caddr_t addr);

static int devmap_device(devmap_handle_t *dhp, struct as *as, caddr_t *addr,
    offset_t off, size_t len, uint_t flags);

static void devmap_get_large_pgsize(devmap_handle_t *dhp, size_t len,
    caddr_t addr, size_t *llen, caddr_t *laddr);

static void devmap_handle_reduce_len(devmap_handle_t *dhp, size_t len);

static void *devmap_alloc_pages(vmem_t *vmp, size_t size, int vmflag);
static void devmap_free_pages(vmem_t *vmp, void *inaddr, size_t size);

static void *devmap_umem_alloc_np(size_t size, size_t flags);
static void devmap_umem_free_np(void *addr, size_t size);

/*
 * routines to lock and unlock underlying segkp segment for
 * KMEM_PAGEABLE type cookies.
 */
static faultcode_t  acquire_kpmem_lock(struct ddi_umem_cookie *, size_t);
static void release_kpmem_lock(struct ddi_umem_cookie *, size_t);

/*
 * Routines to synchronize F_SOFTLOCK and F_INVAL faults for
 * drivers with devmap_access callbacks
 */
static int devmap_softlock_enter(struct devmap_softlock *, size_t,
        enum fault_type);
static void devmap_softlock_exit(struct devmap_softlock *, size_t,
        enum fault_type);

static kmutex_t devmapctx_lock;

static kmutex_t devmap_slock;

/*
 * Initialize the thread callbacks and thread private data.
 */
static struct devmap_ctx *
devmap_ctxinit(dev_t dev, ulong_t id)
{
        struct devmap_ctx       *devctx;
        struct devmap_ctx       *tmp;
        dev_info_t              *dip;

        tmp =  kmem_zalloc(sizeof (struct devmap_ctx), KM_SLEEP);

        mutex_enter(&devmapctx_lock);

        dip = e_ddi_hold_devi_by_dev(dev, 0);
        ASSERT(dip != NULL);
        ddi_release_devi(dip);

        for (devctx = devmapctx_list; devctx != NULL; devctx = devctx->next)
                if ((devctx->dip == dip) && (devctx->id == id))
                        break;

        if (devctx == NULL) {
                devctx = tmp;
                devctx->dip = dip;
                devctx->id = id;
                mutex_init(&devctx->lock, NULL, MUTEX_DEFAULT, NULL);
                cv_init(&devctx->cv, NULL, CV_DEFAULT, NULL);
                devctx->next = devmapctx_list;
                devmapctx_list = devctx;
        } else
                kmem_free(tmp, sizeof (struct devmap_ctx));

        mutex_enter(&devctx->lock);
        devctx->refcnt++;
        mutex_exit(&devctx->lock);
        mutex_exit(&devmapctx_lock);

        return (devctx);
}

/*
 * Timeout callback called if a CPU has not given up the device context
 * within dhp->dh_timeout_length ticks
 */
static void
devmap_ctxto(void *data)
{
        struct devmap_ctx *devctx = data;

        mutex_enter(&devctx->lock);
        /*
         * Set oncpu = 0 so the next mapping trying to get the device context
         * can.
         */
        devctx->oncpu = 0;
        devctx->timeout = 0;
        cv_signal(&devctx->cv);
        mutex_exit(&devctx->lock);
}

/*
 * Create a device segment.
 */
int
segdev_create(struct seg **segpp, void *argsp)
{
        struct seg *seg = *segpp;
        struct segdev_data *sdp;
        struct segdev_crargs *a = (struct segdev_crargs *)argsp;
        devmap_handle_t *dhp = (devmap_handle_t *)a->devmap_data;
        int error;

        /*
         * Since the address space is "write" locked, we
         * don't need the segment lock to protect "segdev" data.
         */
        ASSERT(seg->s_as && AS_WRITE_HELD(seg->s_as));

        hat_map(seg->s_as->a_hat, seg->s_base, seg->s_size, HAT_MAP);

        sdp = sdp_alloc();

        sdp->mapfunc = a->mapfunc;
        sdp->offset = a->offset;
        sdp->prot = a->prot;
        sdp->maxprot = a->maxprot;
        sdp->type = a->type;
        sdp->pageprot = 0;
        sdp->softlockcnt = 0;
        sdp->vpage = NULL;

        if (sdp->mapfunc == NULL)
                sdp->devmap_data = dhp;
        else
                sdp->devmap_data = dhp = NULL;

        sdp->hat_flags = a->hat_flags;
        sdp->hat_attr = a->hat_attr;

        /*
         * Currently, hat_flags supports only HAT_LOAD_NOCONSIST
         */
        ASSERT(!(sdp->hat_flags & ~HAT_LOAD_NOCONSIST));

        /*
         * Hold shadow vnode -- segdev only deals with
         * character (VCHR) devices. We use the common
         * vp to hang pages on.
         */
        sdp->vp = specfind(a->dev, VCHR);
        ASSERT(sdp->vp != NULL);

        seg->s_ops = &segdev_ops;
        seg->s_data = sdp;

        while (dhp != NULL) {
                dhp->dh_seg = seg;
                dhp = dhp->dh_next;
        }

        /*
         * Inform the vnode of the new mapping.
         */
        /*
         * It is ok to use pass sdp->maxprot to ADDMAP rather than to use
         * dhp specific maxprot because spec_addmap does not use maxprot.
         */
        error = fop_addmap(VTOCVP(sdp->vp), sdp->offset,
            seg->s_as, seg->s_base, seg->s_size,
            sdp->prot, sdp->maxprot, sdp->type, CRED(), NULL);

        if (error != 0) {
                sdp->devmap_data = NULL;
                hat_unload(seg->s_as->a_hat, seg->s_base, seg->s_size,
                    HAT_UNLOAD_UNMAP);
        } else {
                /*
                 * Mappings of /dev/null don't count towards the VSZ of a
                 * process.  Mappings of /dev/null have no mapping type.
                 */
                if ((segop_gettype(seg, seg->s_base) & (MAP_SHARED |
                    MAP_PRIVATE)) == 0) {
                        seg->s_as->a_resvsize -= seg->s_size;
                }
        }

        return (error);
}

static struct segdev_data *
sdp_alloc(void)
{
        struct segdev_data *sdp;

        sdp = kmem_zalloc(sizeof (struct segdev_data), KM_SLEEP);
        rw_init(&sdp->lock, NULL, RW_DEFAULT, NULL);

        return (sdp);
}

/*
 * Duplicate seg and return new segment in newseg.
 */
static int
segdev_dup(struct seg *seg, struct seg *newseg)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        struct segdev_data *newsdp;
        devmap_handle_t *dhp = (devmap_handle_t *)sdp->devmap_data;
        size_t npages;
        int ret;

        DEBUGF(3, (CE_CONT, "segdev_dup: dhp %p seg %p\n",
            (void *)dhp, (void *)seg));

        /*
         * Since the address space is "write" locked, we
         * don't need the segment lock to protect "segdev" data.
         */
        ASSERT(seg->s_as && AS_WRITE_HELD(seg->s_as));

        newsdp = sdp_alloc();

        newseg->s_ops = seg->s_ops;
        newseg->s_data = (void *)newsdp;

        VN_HOLD(sdp->vp);
        newsdp->vp      = sdp->vp;
        newsdp->mapfunc = sdp->mapfunc;
        newsdp->offset  = sdp->offset;
        newsdp->pageprot = sdp->pageprot;
        newsdp->prot    = sdp->prot;
        newsdp->maxprot = sdp->maxprot;
        newsdp->type = sdp->type;
        newsdp->hat_attr = sdp->hat_attr;
        newsdp->hat_flags = sdp->hat_flags;
        newsdp->softlockcnt = 0;

        /*
         * Initialize per page data if the segment we are
         * dup'ing has per page information.
         */
        npages = seg_pages(newseg);

        if (sdp->vpage != NULL) {
                size_t nbytes = vpgtob(npages);

                newsdp->vpage = kmem_zalloc(nbytes, KM_SLEEP);
                bcopy(sdp->vpage, newsdp->vpage, nbytes);
        } else
                newsdp->vpage = NULL;

        /*
         * duplicate devmap handles
         */
        if (dhp != NULL) {
                ret = devmap_handle_dup(dhp,
                    (devmap_handle_t **)&newsdp->devmap_data, newseg);
                if (ret != 0) {
                        DEBUGF(1, (CE_CONT,
                            "segdev_dup: ret %x dhp %p seg %p\n",
                            ret, (void *)dhp, (void *)seg));
                        return (ret);
                }
        }

        /*
         * Inform the common vnode of the new mapping.
         */
        return (fop_addmap(VTOCVP(newsdp->vp),
            newsdp->offset, newseg->s_as,
            newseg->s_base, newseg->s_size, newsdp->prot,
            newsdp->maxprot, sdp->type, CRED(), NULL));
}

/*
 * duplicate devmap handles
 */
static int
devmap_handle_dup(devmap_handle_t *dhp, devmap_handle_t **new_dhp,
    struct seg *newseg)
{
        devmap_handle_t *newdhp_save = NULL;
        devmap_handle_t *newdhp = NULL;
        struct devmap_callback_ctl *callbackops;

        while (dhp != NULL) {
                newdhp = kmem_alloc(sizeof (devmap_handle_t), KM_SLEEP);

                /* Need to lock the original dhp while copying if REMAP */
                HOLD_DHP_LOCK(dhp);
                bcopy(dhp, newdhp, sizeof (devmap_handle_t));
                RELE_DHP_LOCK(dhp);
                newdhp->dh_seg = newseg;
                newdhp->dh_next = NULL;
                if (newdhp_save != NULL)
                        newdhp_save->dh_next = newdhp;
                else
                        *new_dhp = newdhp;
                newdhp_save = newdhp;

                callbackops = &newdhp->dh_callbackops;

                if (dhp->dh_softlock != NULL)
                        newdhp->dh_softlock = devmap_softlock_init(
                            newdhp->dh_dev,
                            (ulong_t)callbackops->devmap_access);
                if (dhp->dh_ctx != NULL)
                        newdhp->dh_ctx = devmap_ctxinit(newdhp->dh_dev,
                            (ulong_t)callbackops->devmap_access);

                /*
                 * Initialize dh_lock if we want to do remap.
                 */
                if (newdhp->dh_flags & DEVMAP_ALLOW_REMAP) {
                        mutex_init(&newdhp->dh_lock, NULL, MUTEX_DEFAULT, NULL);
                        newdhp->dh_flags |= DEVMAP_LOCK_INITED;
                }

                if (callbackops->devmap_dup != NULL) {
                        int ret;

                        /*
                         * Call the dup callback so that the driver can
                         * duplicate its private data.
                         */
                        ret = (*callbackops->devmap_dup)(dhp, dhp->dh_pvtp,
                            (devmap_cookie_t *)newdhp, &newdhp->dh_pvtp);

                        if (ret != 0) {
                                /*
                                 * We want to free up this segment as the driver
                                 * has indicated that we can't dup it.  But we
                                 * don't want to call the drivers, devmap_unmap,
                                 * callback function as the driver does not
                                 * think this segment exists. The caller of
                                 * devmap_dup will call seg_free on newseg
                                 * as it was the caller that allocated the
                                 * segment.
                                 */
                                DEBUGF(1, (CE_CONT, "devmap_handle_dup ERROR: "
                                    "newdhp %p dhp %p\n", (void *)newdhp,
                                    (void *)dhp));
                                callbackops->devmap_unmap = NULL;
                                return (ret);
                        }
                }

                dhp = dhp->dh_next;
        }

        return (0);
}

/*
 * Split a segment at addr for length len.
 */
/*ARGSUSED*/
static int
segdev_unmap(struct seg *seg, caddr_t addr, size_t len)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        register struct segdev_data *nsdp;
        register struct seg *nseg;
        register size_t opages;         /* old segment size in pages */
        register size_t npages;         /* new segment size in pages */
        register size_t dpages;         /* pages being deleted (unmapped) */
        register size_t nbytes;
        devmap_handle_t *dhp = (devmap_handle_t *)sdp->devmap_data;
        devmap_handle_t *dhpp;
        devmap_handle_t *newdhp;
        struct devmap_callback_ctl *callbackops;
        caddr_t nbase;
        offset_t off;
        ulong_t nsize;
        size_t mlen, sz;

        DEBUGF(3, (CE_CONT, "segdev_unmap: dhp %p seg %p addr %p len %lx\n",
            (void *)dhp, (void *)seg, (void *)addr, len));

        /*
         * Since the address space is "write" locked, we
         * don't need the segment lock to protect "segdev" data.
         */
        ASSERT(seg->s_as && AS_WRITE_HELD(seg->s_as));

        if ((sz = sdp->softlockcnt) > 0) {
                /*
                 * Fail the unmap if pages are SOFTLOCKed through this mapping.
                 * softlockcnt is protected from change by the as write lock.
                 */
                DEBUGF(1, (CE_CONT, "segdev_unmap: softlockcnt %ld\n", sz));
                return (EAGAIN);
        }

        /*
         * Check for bad sizes
         */
        if (addr < seg->s_base || addr + len > seg->s_base + seg->s_size ||
            (len & PAGEOFFSET) || ((uintptr_t)addr & PAGEOFFSET))
                panic("segdev_unmap");

        if (dhp != NULL) {
                devmap_handle_t *tdhp;
                /*
                 * If large page size was used in hat_devload(),
                 * the same page size must be used in hat_unload().
                 */
                dhpp = tdhp = devmap_find_handle(dhp, addr);
                while (tdhp != NULL) {
                        if (tdhp->dh_flags & DEVMAP_FLAG_LARGE) {
                                break;
                        }
                        tdhp = tdhp->dh_next;
                }
                if (tdhp != NULL) {     /* found a dhp using large pages */
                        size_t slen = len;
                        size_t mlen;
                        size_t soff;

                        soff = (ulong_t)(addr - dhpp->dh_uvaddr);
                        while (slen != 0) {
                                mlen = MIN(slen, (dhpp->dh_len - soff));
                                hat_unload(seg->s_as->a_hat, dhpp->dh_uvaddr,
                                    dhpp->dh_len, HAT_UNLOAD_UNMAP);
                                dhpp = dhpp->dh_next;
                                ASSERT(slen >= mlen);
                                slen -= mlen;
                                soff = 0;
                        }
                } else
                        hat_unload(seg->s_as->a_hat, addr, len,
                            HAT_UNLOAD_UNMAP);
        } else {
                /*
                 * Unload any hardware translations in the range
                 * to be taken out.
                 */
                hat_unload(seg->s_as->a_hat, addr, len, HAT_UNLOAD_UNMAP);
        }

        /*
         * get the user offset which will used in the driver callbacks
         */
        off = sdp->offset + (offset_t)(addr - seg->s_base);

        /*
         * Inform the vnode of the unmapping.
         */
        ASSERT(sdp->vp != NULL);
        (void) fop_delmap(VTOCVP(sdp->vp), off, seg->s_as, addr, len,
            sdp->prot, sdp->maxprot, sdp->type, CRED(), NULL);

        /*
         * Check for entire segment
         */
        if (addr == seg->s_base && len == seg->s_size) {
                seg_free(seg);
                return (0);
        }

        opages = seg_pages(seg);
        dpages = btop(len);
        npages = opages - dpages;

        /*
         * Check for beginning of segment
         */
        if (addr == seg->s_base) {
                if (sdp->vpage != NULL) {
                        register struct vpage *ovpage;

                        ovpage = sdp->vpage;    /* keep pointer to vpage */

                        nbytes = vpgtob(npages);
                        sdp->vpage = kmem_alloc(nbytes, KM_SLEEP);
                        bcopy(&ovpage[dpages], sdp->vpage, nbytes);

                        /* free up old vpage */
                        kmem_free(ovpage, vpgtob(opages));
                }

                /*
                 * free devmap handles from the beginning of the mapping.
                 */
                if (dhp != NULL)
                        devmap_handle_unmap_head(dhp, len);

                sdp->offset += (offset_t)len;

                seg->s_base += len;
                seg->s_size -= len;

                return (0);
        }

        /*
         * Check for end of segment
         */
        if (addr + len == seg->s_base + seg->s_size) {
                if (sdp->vpage != NULL) {
                        register struct vpage *ovpage;

                        ovpage = sdp->vpage;    /* keep pointer to vpage */

                        nbytes = vpgtob(npages);
                        sdp->vpage = kmem_alloc(nbytes, KM_SLEEP);
                        bcopy(ovpage, sdp->vpage, nbytes);

                        /* free up old vpage */
                        kmem_free(ovpage, vpgtob(opages));
                }
                seg->s_size -= len;

                /*
                 * free devmap handles from addr to the end of the mapping.
                 */
                if (dhp != NULL)
                        devmap_handle_unmap_tail(dhp, addr);

                return (0);
        }

        /*
         * The section to go is in the middle of the segment,
         * have to make it into two segments.  nseg is made for
         * the high end while seg is cut down at the low end.
         */
        nbase = addr + len;                             /* new seg base */
        nsize = (seg->s_base + seg->s_size) - nbase;    /* new seg size */
        seg->s_size = addr - seg->s_base;               /* shrink old seg */
        nseg = seg_alloc(seg->s_as, nbase, nsize);
        if (nseg == NULL)
                panic("segdev_unmap seg_alloc");

        DEBUGF(3, (CE_CONT, "segdev_unmap: segdev_dup seg %p nseg %p\n",
            (void *)seg, (void *)nseg));
        nsdp = sdp_alloc();

        nseg->s_ops = seg->s_ops;
        nseg->s_data = (void *)nsdp;

        VN_HOLD(sdp->vp);
        nsdp->mapfunc = sdp->mapfunc;
        nsdp->offset = sdp->offset + (offset_t)(nseg->s_base - seg->s_base);
        nsdp->vp        = sdp->vp;
        nsdp->pageprot = sdp->pageprot;
        nsdp->prot      = sdp->prot;
        nsdp->maxprot = sdp->maxprot;
        nsdp->type = sdp->type;
        nsdp->hat_attr = sdp->hat_attr;
        nsdp->hat_flags = sdp->hat_flags;
        nsdp->softlockcnt = 0;

        /*
         * Initialize per page data if the segment we are
         * dup'ing has per page information.
         */
        if (sdp->vpage != NULL) {
                /* need to split vpage into two arrays */
                register size_t nnbytes;
                register size_t nnpages;
                register struct vpage *ovpage;

                ovpage = sdp->vpage;            /* keep pointer to vpage */

                npages = seg_pages(seg);        /* seg has shrunk */
                nbytes = vpgtob(npages);
                nnpages = seg_pages(nseg);
                nnbytes = vpgtob(nnpages);

                sdp->vpage = kmem_alloc(nbytes, KM_SLEEP);
                bcopy(ovpage, sdp->vpage, nbytes);

                nsdp->vpage = kmem_alloc(nnbytes, KM_SLEEP);
                bcopy(&ovpage[npages + dpages], nsdp->vpage, nnbytes);

                /* free up old vpage */
                kmem_free(ovpage, vpgtob(opages));
        } else
                nsdp->vpage = NULL;

        /*
         * unmap dhps.
         */
        if (dhp == NULL) {
                nsdp->devmap_data = NULL;
                return (0);
        }
        while (dhp != NULL) {
                callbackops = &dhp->dh_callbackops;
                DEBUGF(3, (CE_CONT, "unmap: dhp %p addr %p uvaddr %p len %lx\n",
                    (void *)dhp, (void *)addr,
                    (void *)dhp->dh_uvaddr, dhp->dh_len));

                if (addr == (dhp->dh_uvaddr + dhp->dh_len)) {
                        dhpp = dhp->dh_next;
                        dhp->dh_next = NULL;
                        dhp = dhpp;
                } else if (addr > (dhp->dh_uvaddr + dhp->dh_len)) {
                        dhp = dhp->dh_next;
                } else if (addr > dhp->dh_uvaddr &&
                    (addr + len) < (dhp->dh_uvaddr + dhp->dh_len)) {
                        /*
                         * <addr, addr+len> is enclosed by dhp.
                         * create a newdhp that begins at addr+len and
                         * ends at dhp->dh_uvaddr+dhp->dh_len.
                         */
                        newdhp = kmem_alloc(sizeof (devmap_handle_t), KM_SLEEP);
                        HOLD_DHP_LOCK(dhp);
                        bcopy(dhp, newdhp, sizeof (devmap_handle_t));
                        RELE_DHP_LOCK(dhp);
                        newdhp->dh_seg = nseg;
                        newdhp->dh_next = dhp->dh_next;
                        if (dhp->dh_softlock != NULL)
                                newdhp->dh_softlock = devmap_softlock_init(
                                    newdhp->dh_dev,
                                    (ulong_t)callbackops->devmap_access);
                        if (dhp->dh_ctx != NULL)
                                newdhp->dh_ctx = devmap_ctxinit(newdhp->dh_dev,
                                    (ulong_t)callbackops->devmap_access);
                        if (newdhp->dh_flags & DEVMAP_LOCK_INITED) {
                                mutex_init(&newdhp->dh_lock,
                                    NULL, MUTEX_DEFAULT, NULL);
                        }
                        if (callbackops->devmap_unmap != NULL)
                                (*callbackops->devmap_unmap)(dhp, dhp->dh_pvtp,
                                    off, len, dhp, &dhp->dh_pvtp,
                                    newdhp, &newdhp->dh_pvtp);
                        mlen = len + (addr - dhp->dh_uvaddr);
                        devmap_handle_reduce_len(newdhp, mlen);
                        nsdp->devmap_data = newdhp;
                        /* XX Changing len should recalculate LARGE flag */
                        dhp->dh_len = addr - dhp->dh_uvaddr;
                        dhpp = dhp->dh_next;
                        dhp->dh_next = NULL;
                        dhp = dhpp;
                } else if ((addr > dhp->dh_uvaddr) &&
                    ((addr + len) >= (dhp->dh_uvaddr + dhp->dh_len))) {
                        mlen = dhp->dh_len + dhp->dh_uvaddr - addr;
                        /*
                         * <addr, addr+len> spans over dhps.
                         */
                        if (callbackops->devmap_unmap != NULL)
                                (*callbackops->devmap_unmap)(dhp, dhp->dh_pvtp,
                                    off, mlen, (devmap_cookie_t *)dhp,
                                    &dhp->dh_pvtp, NULL, NULL);
                        /* XX Changing len should recalculate LARGE flag */
                        dhp->dh_len = addr - dhp->dh_uvaddr;
                        dhpp = dhp->dh_next;
                        dhp->dh_next = NULL;
                        dhp = dhpp;
                        nsdp->devmap_data = dhp;
                } else if ((addr + len) >= (dhp->dh_uvaddr + dhp->dh_len)) {
                        /*
                         * dhp is enclosed by <addr, addr+len>.
                         */
                        dhp->dh_seg = nseg;
                        nsdp->devmap_data = dhp;
                        dhp = devmap_handle_unmap(dhp);
                        nsdp->devmap_data = dhp; /* XX redundant? */
                } else if (((addr + len) > dhp->dh_uvaddr) &&
                    ((addr + len) < (dhp->dh_uvaddr + dhp->dh_len))) {
                        mlen = addr + len - dhp->dh_uvaddr;
                        if (callbackops->devmap_unmap != NULL)
                                (*callbackops->devmap_unmap)(dhp, dhp->dh_pvtp,
                                    dhp->dh_uoff, mlen, NULL,
                                    NULL, dhp, &dhp->dh_pvtp);
                        devmap_handle_reduce_len(dhp, mlen);
                        nsdp->devmap_data = dhp;
                        dhp->dh_seg = nseg;
                        dhp = dhp->dh_next;
                } else {
                        dhp->dh_seg = nseg;
                        dhp = dhp->dh_next;
                }
        }
        return (0);
}

/*
 * Utility function handles reducing the length of a devmap handle during unmap
 * Note that is only used for unmapping the front portion of the handler,
 * i.e., we are bumping up the offset/pfn etc up by len
 * Do not use if reducing length at the tail.
 */
static void
devmap_handle_reduce_len(devmap_handle_t *dhp, size_t len)
{
        struct ddi_umem_cookie *cp;
        struct devmap_pmem_cookie *pcp;
        /*
         * adjust devmap handle fields
         */
        ASSERT(len < dhp->dh_len);

        /* Make sure only page-aligned changes are done */
        ASSERT((len & PAGEOFFSET) == 0);

        dhp->dh_len -= len;
        dhp->dh_uoff += (offset_t)len;
        dhp->dh_roff += (offset_t)len;
        dhp->dh_uvaddr += len;
        /* Need to grab dhp lock if REMAP */
        HOLD_DHP_LOCK(dhp);
        cp = dhp->dh_cookie;
        if (!(dhp->dh_flags & DEVMAP_MAPPING_INVALID)) {
                if (cookie_is_devmem(cp)) {
                        dhp->dh_pfn += btop(len);
                } else if (cookie_is_pmem(cp)) {
                        pcp = (struct devmap_pmem_cookie *)dhp->dh_pcookie;
                        ASSERT((dhp->dh_roff & PAGEOFFSET) == 0 &&
                            dhp->dh_roff < ptob(pcp->dp_npages));
                } else {
                        ASSERT(dhp->dh_roff < cp->size);
                        ASSERT(dhp->dh_cvaddr >= cp->cvaddr &&
                            dhp->dh_cvaddr < (cp->cvaddr + cp->size));
                        ASSERT((dhp->dh_cvaddr + len) <=
                            (cp->cvaddr + cp->size));

                        dhp->dh_cvaddr += len;
                }
        }
        /* XXX - Should recalculate the DEVMAP_FLAG_LARGE after changes */
        RELE_DHP_LOCK(dhp);
}

/*
 * Free devmap handle, dhp.
 * Return the next devmap handle on the linked list.
 */
static devmap_handle_t *
devmap_handle_unmap(devmap_handle_t *dhp)
{
        struct devmap_callback_ctl *callbackops = &dhp->dh_callbackops;
        struct segdev_data *sdp = (struct segdev_data *)dhp->dh_seg->s_data;
        devmap_handle_t *dhpp = (devmap_handle_t *)sdp->devmap_data;

        ASSERT(dhp != NULL);

        /*
         * before we free up dhp, call the driver's devmap_unmap entry point
         * to free resources allocated for this dhp.
         */
        if (callbackops->devmap_unmap != NULL) {
                (*callbackops->devmap_unmap)(dhp, dhp->dh_pvtp, dhp->dh_uoff,
                    dhp->dh_len, NULL, NULL, NULL, NULL);
        }

        if (dhpp == dhp) {      /* releasing first dhp, change sdp data */
                sdp->devmap_data = dhp->dh_next;
        } else {
                while (dhpp->dh_next != dhp) {
                        dhpp = dhpp->dh_next;
                }
                dhpp->dh_next = dhp->dh_next;
        }
        dhpp = dhp->dh_next;    /* return value is next dhp in chain */

        if (dhp->dh_softlock != NULL)
                devmap_softlock_rele(dhp);

        if (dhp->dh_ctx != NULL)
                devmap_ctx_rele(dhp);

        if (dhp->dh_flags & DEVMAP_LOCK_INITED) {
                mutex_destroy(&dhp->dh_lock);
        }
        kmem_free(dhp, sizeof (devmap_handle_t));

        return (dhpp);
}

/*
 * Free complete devmap handles from dhp for len bytes
 * dhp can be either the first handle or a subsequent handle
 */
static void
devmap_handle_unmap_head(devmap_handle_t *dhp, size_t len)
{
        struct devmap_callback_ctl *callbackops;

        /*
         * free the devmap handles covered by len.
         */
        while (len >= dhp->dh_len) {
                len -= dhp->dh_len;
                dhp = devmap_handle_unmap(dhp);
        }
        if (len != 0) { /* partial unmap at head of first remaining dhp */
                callbackops = &dhp->dh_callbackops;

                /*
                 * Call the unmap callback so the drivers can make
                 * adjustment on its private data.
                 */
                if (callbackops->devmap_unmap != NULL)
                        (*callbackops->devmap_unmap)(dhp, dhp->dh_pvtp,
                            dhp->dh_uoff, len, NULL, NULL, dhp, &dhp->dh_pvtp);
                devmap_handle_reduce_len(dhp, len);
        }
}

/*
 * Free devmap handles to truncate  the mapping after addr
 * RFE: Simpler to pass in dhp pointing at correct dhp (avoid find again)
 *      Also could then use the routine in middle unmap case too
 */
static void
devmap_handle_unmap_tail(devmap_handle_t *dhp, caddr_t addr)
{
        register struct seg *seg = dhp->dh_seg;
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        register devmap_handle_t *dhph = (devmap_handle_t *)sdp->devmap_data;
        struct devmap_callback_ctl *callbackops;
        register devmap_handle_t *dhpp;
        size_t maplen;
        ulong_t off;
        size_t len;

        maplen = (size_t)(addr - dhp->dh_uvaddr);
        dhph = devmap_find_handle(dhph, addr);

        while (dhph != NULL) {
                if (maplen == 0) {
                        dhph =  devmap_handle_unmap(dhph);
                } else {
                        callbackops = &dhph->dh_callbackops;
                        len = dhph->dh_len - maplen;
                        off = (ulong_t)sdp->offset + (addr - seg->s_base);
                        /*
                         * Call the unmap callback so the driver
                         * can make adjustments on its private data.
                         */
                        if (callbackops->devmap_unmap != NULL)
                                (*callbackops->devmap_unmap)(dhph,
                                    dhph->dh_pvtp, off, len,
                                    (devmap_cookie_t *)dhph,
                                    &dhph->dh_pvtp, NULL, NULL);
                        /* XXX Reducing len needs to recalculate LARGE flag */
                        dhph->dh_len = maplen;
                        maplen = 0;
                        dhpp = dhph->dh_next;
                        dhph->dh_next = NULL;
                        dhph = dhpp;
                }
        } /* end while */
}

/*
 * Free a segment.
 */
static void
segdev_free(struct seg *seg)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        devmap_handle_t *dhp = (devmap_handle_t *)sdp->devmap_data;

        DEBUGF(3, (CE_CONT, "segdev_free: dhp %p seg %p\n",
            (void *)dhp, (void *)seg));

        /*
         * Since the address space is "write" locked, we
         * don't need the segment lock to protect "segdev" data.
         */
        ASSERT(seg->s_as && AS_WRITE_HELD(seg->s_as));

        while (dhp != NULL)
                dhp = devmap_handle_unmap(dhp);

        VN_RELE(sdp->vp);
        if (sdp->vpage != NULL)
                kmem_free(sdp->vpage, vpgtob(seg_pages(seg)));

        rw_destroy(&sdp->lock);
        kmem_free(sdp, sizeof (*sdp));
}

static void
free_devmap_handle(devmap_handle_t *dhp)
{
        register devmap_handle_t *dhpp;

        /*
         * free up devmap handle
         */
        while (dhp != NULL) {
                dhpp = dhp->dh_next;
                if (dhp->dh_flags & DEVMAP_LOCK_INITED) {
                        mutex_destroy(&dhp->dh_lock);
                }

                if (dhp->dh_softlock != NULL)
                        devmap_softlock_rele(dhp);

                if (dhp->dh_ctx != NULL)
                        devmap_ctx_rele(dhp);

                kmem_free(dhp, sizeof (devmap_handle_t));
                dhp = dhpp;
        }
}

/*
 * routines to lock and unlock underlying segkp segment for
 * KMEM_PAGEABLE type cookies.
 * segkp only allows a single pending F_SOFTLOCK
 * we keep track of number of locks in the cookie so we can
 * have multiple pending faults and manage the calls to segkp.
 * RFE: if segkp supports either pagelock or can support multiple
 * calls to F_SOFTLOCK, then these routines can go away.
 *      If pagelock, segdev_faultpage can fault on a page by page basis
 *              and simplifies the code quite a bit.
 *      if multiple calls allowed but not partial ranges, then need for
 *      cookie->lock and locked count goes away, code can call as_fault directly
 */
static faultcode_t
acquire_kpmem_lock(struct ddi_umem_cookie *cookie, size_t npages)
{
        int err = 0;
        ASSERT(cookie_is_kpmem(cookie));
        /*
         * Fault in pages in segkp with F_SOFTLOCK.
         * We want to hold the lock until all pages have been loaded.
         * segkp only allows single caller to hold SOFTLOCK, so cookie
         * holds a count so we dont call into segkp multiple times
         */
        mutex_enter(&cookie->lock);

        /*
         * Check for overflow in locked field
         */
        if ((UINT32_MAX - cookie->locked) < npages) {
                err = FC_MAKE_ERR(ENOMEM);
        } else if (cookie->locked == 0) {
                /* First time locking */
                err = as_fault(kas.a_hat, &kas, cookie->cvaddr,
                    cookie->size, F_SOFTLOCK, PROT_READ|PROT_WRITE);
        }
        if (!err) {
                cookie->locked += npages;
        }
        mutex_exit(&cookie->lock);
        return (err);
}

static void
release_kpmem_lock(struct ddi_umem_cookie *cookie, size_t npages)
{
        mutex_enter(&cookie->lock);
        ASSERT(cookie_is_kpmem(cookie));
        ASSERT(cookie->locked >= npages);
        cookie->locked -= (uint_t)npages;
        if (cookie->locked == 0) {
                /* Last unlock */
                if (as_fault(kas.a_hat, &kas, cookie->cvaddr,
                    cookie->size, F_SOFTUNLOCK, PROT_READ|PROT_WRITE))
                        panic("segdev releasing kpmem lock %p", (void *)cookie);
        }
        mutex_exit(&cookie->lock);
}

/*
 * Routines to synchronize F_SOFTLOCK and F_INVAL faults for
 * drivers with devmap_access callbacks
 * slock->softlocked basically works like a rw lock
 *      -ve counts => F_SOFTLOCK in progress
 *      +ve counts => F_INVAL/F_PROT in progress
 * We allow only one F_SOFTLOCK at a time
 * but can have multiple pending F_INVAL/F_PROT calls
 *
 * This routine waits using cv_wait_sig so killing processes is more graceful
 * Returns EINTR if coming out of this routine due to a signal, 0 otherwise
 */
static int devmap_softlock_enter(
        struct devmap_softlock *slock,
        size_t npages,
        enum fault_type type)
{
        if (npages == 0)
                return (0);
        mutex_enter(&(slock->lock));
        switch (type) {
        case F_SOFTLOCK :
                while (slock->softlocked) {
                        if (cv_wait_sig(&(slock)->cv, &(slock)->lock) == 0) {
                                /* signalled */
                                mutex_exit(&(slock->lock));
                                return (EINTR);
                        }
                }
                slock->softlocked -= npages; /* -ve count => locked */
                break;
        case F_INVAL :
        case F_PROT :
                while (slock->softlocked < 0)
                        if (cv_wait_sig(&(slock)->cv, &(slock)->lock) == 0) {
                                /* signalled */
                                mutex_exit(&(slock->lock));
                                return (EINTR);
                        }
                slock->softlocked += npages; /* +ve count => f_invals */
                break;
        default:
                ASSERT(0);
        }
        mutex_exit(&(slock->lock));
        return (0);
}

static void devmap_softlock_exit(
        struct devmap_softlock *slock,
        size_t npages,
        enum fault_type type)
{
        if (slock == NULL)
                return;
        mutex_enter(&(slock->lock));
        switch (type) {
        case F_SOFTLOCK :
                ASSERT(-slock->softlocked >= npages);
                slock->softlocked += npages;    /* -ve count is softlocked */
                if (slock->softlocked == 0)
                        cv_signal(&slock->cv);
                break;
        case F_INVAL :
        case F_PROT:
                ASSERT(slock->softlocked >= npages);
                slock->softlocked -= npages;
                if (slock->softlocked == 0)
                        cv_signal(&slock->cv);
                break;
        default:
                ASSERT(0);
        }
        mutex_exit(&(slock->lock));
}

/*
 * Do a F_SOFTUNLOCK call over the range requested.
 * The range must have already been F_SOFTLOCK'ed.
 * The segment lock should be held, (but not the segment private lock?)
 *  The softunlock code below does not adjust for large page sizes
 *      assumes the caller already did any addr/len adjustments for
 *      pagesize mappings before calling.
 */
/*ARGSUSED*/
static void
segdev_softunlock(
        struct hat *hat,                /* the hat */
        struct seg *seg,                /* seg_dev of interest */
        caddr_t addr,                   /* base address of range */
        size_t len,                     /* number of bytes */
        enum seg_rw rw)                 /* type of access at fault */
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        devmap_handle_t *dhp_head = (devmap_handle_t *)sdp->devmap_data;

        DEBUGF(3, (CE_CONT, "segdev_softunlock: dhp %p lockcnt %lx "
            "addr %p len %lx\n",
            (void *)dhp_head, sdp->softlockcnt, (void *)addr, len));

        hat_unlock(hat, addr, len);

        if (dhp_head != NULL) {
                devmap_handle_t *dhp;
                size_t mlen;
                size_t tlen = len;
                ulong_t off;

                dhp = devmap_find_handle(dhp_head, addr);
                ASSERT(dhp != NULL);

                off = (ulong_t)(addr - dhp->dh_uvaddr);
                while (tlen != 0) {
                        mlen = MIN(tlen, (dhp->dh_len - off));

                        /*
                         * unlock segkp memory, locked during F_SOFTLOCK
                         */
                        if (dhp_is_kpmem(dhp)) {
                                release_kpmem_lock(
                                    (struct ddi_umem_cookie *)dhp->dh_cookie,
                                    btopr(mlen));
                        }

                        /*
                         * Do the softlock accounting for devmap_access
                         */
                        if (dhp->dh_callbackops.devmap_access != NULL) {
                                devmap_softlock_exit(dhp->dh_softlock,
                                    btopr(mlen), F_SOFTLOCK);
                        }

                        tlen -= mlen;
                        dhp = dhp->dh_next;
                        off = 0;
                }
        }

        mutex_enter(&freemem_lock);
        ASSERT(sdp->softlockcnt >= btopr(len));
        sdp->softlockcnt -= btopr(len);
        mutex_exit(&freemem_lock);
        if (sdp->softlockcnt == 0) {
                /*
                 * All SOFTLOCKS are gone. Wakeup any waiting
                 * unmappers so they can try again to unmap.
                 * Check for waiters first without the mutex
                 * held so we don't always grab the mutex on
                 * softunlocks.
                 */
                if (AS_ISUNMAPWAIT(seg->s_as)) {
                        mutex_enter(&seg->s_as->a_contents);
                        if (AS_ISUNMAPWAIT(seg->s_as)) {
                                AS_CLRUNMAPWAIT(seg->s_as);
                                cv_broadcast(&seg->s_as->a_cv);
                        }
                        mutex_exit(&seg->s_as->a_contents);
                }
        }

}

/*
 * Handle fault for a single page.
 * Done in a separate routine so we can handle errors more easily.
 * This routine is called only from segdev_faultpages()
 * when looping over the range of addresses requested. The segment lock is held.
 */
static faultcode_t
segdev_faultpage(
        struct hat *hat,                /* the hat */
        struct seg *seg,                /* seg_dev of interest */
        caddr_t addr,                   /* address in as */
        struct vpage *vpage,            /* pointer to vpage for seg, addr */
        enum fault_type type,           /* type of fault */
        enum seg_rw rw,                 /* type of access at fault */
        devmap_handle_t *dhp)           /* devmap handle if any for this page */
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        uint_t prot;
        pfn_t pfnum = PFN_INVALID;
        uoff_t offset;
        uint_t hat_flags;
        dev_info_t *dip;

        DEBUGF(8, (CE_CONT, "segdev_faultpage: dhp %p seg %p addr %p \n",
            (void *)dhp, (void *)seg, (void *)addr));

        /*
         * Initialize protection value for this page.
         * If we have per page protection values check it now.
         */
        if (sdp->pageprot) {
                uint_t protchk;

                switch (rw) {
                case S_READ:
                        protchk = PROT_READ;
                        break;
                case S_WRITE:
                        protchk = PROT_WRITE;
                        break;
                case S_EXEC:
                        protchk = PROT_EXEC;
                        break;
                case S_OTHER:
                default:
                        protchk = PROT_READ | PROT_WRITE | PROT_EXEC;
                        break;
                }

                prot = VPP_PROT(vpage);
                if ((prot & protchk) == 0)
                        return (FC_PROT);       /* illegal access type */
        } else {
                prot = sdp->prot;
                /* caller has already done segment level protection check */
        }

        if (type == F_SOFTLOCK) {
                mutex_enter(&freemem_lock);
                sdp->softlockcnt++;
                mutex_exit(&freemem_lock);
        }

        hat_flags = ((type == F_SOFTLOCK) ? HAT_LOAD_LOCK : HAT_LOAD);
        offset = sdp->offset + (uoff_t)(addr - seg->s_base);
        /*
         * In the devmap framework, sdp->mapfunc is set to NULL.  we can get
         * pfnum from dhp->dh_pfn (at beginning of segment) and offset from
         * seg->s_base.
         */
        if (dhp == NULL) {
                /* If segment has devmap_data, then dhp should be non-NULL */
                ASSERT(sdp->devmap_data == NULL);
                pfnum = (pfn_t)cdev_mmap(sdp->mapfunc, sdp->vp->v_rdev,
                    (off_t)offset, prot);
                prot |= sdp->hat_attr;
        } else {
                ulong_t off;
                struct ddi_umem_cookie *cp;
                struct devmap_pmem_cookie *pcp;

                /* ensure the dhp passed in contains addr. */
                ASSERT(dhp == devmap_find_handle(
                    (devmap_handle_t *)sdp->devmap_data, addr));

                off = addr - dhp->dh_uvaddr;

                /*
                 * This routine assumes that the caller makes sure that the
                 * fields in dhp used below are unchanged due to remap during
                 * this call. Caller does HOLD_DHP_LOCK if neeed
                 */
                cp = dhp->dh_cookie;
                if (dhp->dh_flags & DEVMAP_MAPPING_INVALID) {
                        pfnum = PFN_INVALID;
                } else if (cookie_is_devmem(cp)) {
                        pfnum = dhp->dh_pfn + btop(off);
                } else if (cookie_is_pmem(cp)) {
                        pcp = (struct devmap_pmem_cookie *)dhp->dh_pcookie;
                        ASSERT((dhp->dh_roff & PAGEOFFSET) == 0 &&
                            dhp->dh_roff < ptob(pcp->dp_npages));
                        pfnum = page_pptonum(
                            pcp->dp_pparray[btop(off + dhp->dh_roff)]);
                } else {
                        ASSERT(dhp->dh_roff < cp->size);
                        ASSERT(dhp->dh_cvaddr >= cp->cvaddr &&
                            dhp->dh_cvaddr < (cp->cvaddr + cp->size));
                        ASSERT((dhp->dh_cvaddr + off) <=
                            (cp->cvaddr + cp->size));
                        ASSERT((dhp->dh_cvaddr + off + PAGESIZE) <=
                            (cp->cvaddr + cp->size));

                        switch (cp->type) {
                        case UMEM_LOCKED :
                                if (cp->pparray != NULL) {
                                        ASSERT((dhp->dh_roff &
                                            PAGEOFFSET) == 0);
                                        pfnum = page_pptonum(
                                            cp->pparray[btop(off +
                                            dhp->dh_roff)]);
                                } else {
                                        pfnum = hat_getpfnum(
                                            ((proc_t *)cp->procp)->p_as->a_hat,
                                            cp->cvaddr + off);
                                }
                        break;
                        case UMEM_TRASH :
                                pfnum = page_pptonum(trashpp);
                                /*
                                 * We should set hat_flags to HAT_NOFAULT also
                                 * However, not all hat layers implement this
                                 */
                                break;
                        case KMEM_PAGEABLE:
                        case KMEM_NON_PAGEABLE:
                                pfnum = hat_getpfnum(kas.a_hat,
                                    dhp->dh_cvaddr + off);
                                break;
                        default :
                                pfnum = PFN_INVALID;
                                break;
                        }
                }
                prot |= dhp->dh_hat_attr;
        }
        if (pfnum == PFN_INVALID) {
                return (FC_MAKE_ERR(EFAULT));
        }
        /* prot should already be OR'ed in with hat_attributes if needed */

        DEBUGF(9, (CE_CONT, "segdev_faultpage: pfnum %lx memory %x "
            "prot %x flags %x\n", pfnum, pf_is_memory(pfnum), prot, hat_flags));

        if (pf_is_memory(pfnum) || (dhp != NULL)) {
                /*
                 * It's not _really_ required here to pass sdp->hat_flags
                 * to hat_devload even though we do it.
                 * This is because hat figures it out DEVMEM mappings
                 * are non-consistent, anyway.
                 */
                hat_devload(hat, addr, PAGESIZE, pfnum,
                    prot, hat_flags | sdp->hat_flags);
                return (0);
        }

        /*
         * Fall through to the case where devmap is not used and need to call
         * up the device tree to set up the mapping
         */

        dip = VTOS(VTOCVP(sdp->vp))->s_dip;
        ASSERT(dip);

        /*
         * When calling ddi_map_fault, we do not OR in sdp->hat_attr
         * This is because this calls drivers which may not expect
         * prot to have any other values than PROT_ALL
         * The root nexus driver has a hack to peek into the segment
         * structure and then OR in sdp->hat_attr.
         * XX In case the bus_ops interfaces are ever revisited
         * we need to fix this. prot should include other hat attributes
         */
        if (ddi_map_fault(dip, hat, seg, addr, NULL, pfnum, prot & PROT_ALL,
            (uint_t)(type == F_SOFTLOCK)) != DDI_SUCCESS) {
                return (FC_MAKE_ERR(EFAULT));
        }
        return (0);
}

static faultcode_t
segdev_fault(
        struct hat *hat,                /* the hat */
        struct seg *seg,                /* the seg_dev of interest */
        caddr_t addr,                   /* the address of the fault */
        size_t len,                     /* the length of the range */
        enum fault_type type,           /* type of fault */
        enum seg_rw rw)                 /* type of access at fault */
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        devmap_handle_t *dhp_head = (devmap_handle_t *)sdp->devmap_data;
        devmap_handle_t *dhp;
        struct devmap_softlock *slock = NULL;
        ulong_t slpage = 0;
        ulong_t off;
        caddr_t maddr = addr;
        int err;
        int err_is_faultcode = 0;

        DEBUGF(7, (CE_CONT, "segdev_fault: dhp_head %p seg %p "
            "addr %p len %lx type %x\n",
            (void *)dhp_head, (void *)seg, (void *)addr, len, type));

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        /* Handle non-devmap case */
        if (dhp_head == NULL)
                return (segdev_faultpages(hat, seg, addr, len, type, rw, NULL));

        /* Find devmap handle */
        if ((dhp = devmap_find_handle(dhp_head, addr)) == NULL)
                return (FC_NOMAP);

        /*
         * The seg_dev driver does not implement copy-on-write,
         * and always loads translations with maximal allowed permissions
         * but we got an fault trying to access the device.
         * Servicing the fault is not going to result in any better result
         * RFE: If we want devmap_access callbacks to be involved in F_PROT
         *      faults, then the code below is written for that
         *      Pending resolution of the following:
         *      - determine if the F_INVAL/F_SOFTLOCK syncing
         *      is needed for F_PROT also or not. The code below assumes it does
         *      - If driver sees F_PROT and calls devmap_load with same type,
         *      then segdev_faultpages will fail with FC_PROT anyway, need to
         *      change that so calls from devmap_load to segdev_faultpages for
         *      F_PROT type are retagged to F_INVAL.
         * RFE: Today we dont have drivers that use devmap and want to handle
         *      F_PROT calls. The code in segdev_fault* is written to allow
         *      this case but is not tested. A driver that needs this capability
         *      should be able to remove the short-circuit case; resolve the
         *      above issues and "should" work.
         */
        if (type == F_PROT) {
                return (FC_PROT);
        }

        /*
         * Loop through dhp list calling devmap_access or segdev_faultpages for
         * each devmap handle.
         * drivers which implement devmap_access can interpose on faults and do
         * device-appropriate special actions before calling devmap_load.
         */

        /*
         * Unfortunately, this simple loop has turned out to expose a variety
         * of complex problems which results in the following convoluted code.
         *
         * First, a desire to handle a serialization of F_SOFTLOCK calls
         * to the driver within the framework.
         *      This results in a dh_softlock structure that is on a per device
         *      (or device instance) basis and serializes devmap_access calls.
         *      Ideally we would need to do this for underlying
         *      memory/device regions that are being faulted on
         *      but that is hard to identify and with REMAP, harder
         * Second, a desire to serialize F_INVAL(and F_PROT) calls w.r.t.
         *      to F_SOFTLOCK calls to the driver.
         * These serializations are to simplify the driver programmer model.
         * To support these two features, the code first goes through the
         *      devmap handles and counts the pages (slpage) that are covered
         *      by devmap_access callbacks.
         * This part ends with a devmap_softlock_enter call
         *      which allows only one F_SOFTLOCK active on a device instance,
         *      but multiple F_INVAL/F_PROTs can be active except when a
         *      F_SOFTLOCK is active
         *
         * Next, we dont short-circuit the fault code upfront to call
         *      segdev_softunlock for F_SOFTUNLOCK, because we must use
         *      the same length when we softlock and softunlock.
         *
         *      -Hat layers may not support softunlocking lengths less than the
         *      original length when there is large page support.
         *      -kpmem locking is dependent on keeping the lengths same.
         *      -if drivers handled F_SOFTLOCK, they probably also expect to
         *              see an F_SOFTUNLOCK of the same length
         *      Hence, if extending lengths during softlock,
         *      softunlock has to make the same adjustments and goes through
         *      the same loop calling segdev_faultpages/segdev_softunlock
         *      But some of the synchronization and error handling is different
         */

        if (type != F_SOFTUNLOCK) {
                devmap_handle_t *dhpp = dhp;
                size_t slen = len;

                /*
                 * Calculate count of pages that are :
                 * a) within the (potentially extended) fault region
                 * b) AND covered by devmap handle with devmap_access
                 */
                off = (ulong_t)(addr - dhpp->dh_uvaddr);
                while (slen != 0) {
                        size_t mlen;

                        /*
                         * Softlocking on a region that allows remap is
                         * unsupported due to unresolved locking issues
                         * XXX: unclear what these are?
                         *      One potential is that if there is a pending
                         *      softlock, then a remap should not be allowed
                         *      until the unlock is done. This is easily
                         *      fixed by returning error in devmap*remap on
                         *      checking the dh->dh_softlock->softlocked value
                         */
                        if ((type == F_SOFTLOCK) &&
                            (dhpp->dh_flags & DEVMAP_ALLOW_REMAP)) {
                                return (FC_NOSUPPORT);
                        }

                        mlen = MIN(slen, (dhpp->dh_len - off));
                        if (dhpp->dh_callbackops.devmap_access) {
                                size_t llen;
                                caddr_t laddr;
                                /*
                                 * use extended length for large page mappings
                                 */
                                HOLD_DHP_LOCK(dhpp);
                                if ((sdp->pageprot == 0) &&
                                    (dhpp->dh_flags & DEVMAP_FLAG_LARGE)) {
                                        devmap_get_large_pgsize(dhpp,
                                            mlen, maddr, &llen, &laddr);
                                } else {
                                        llen = mlen;
                                }
                                RELE_DHP_LOCK(dhpp);

                                slpage += btopr(llen);
                                slock = dhpp->dh_softlock;
                        }
                        maddr += mlen;
                        ASSERT(slen >= mlen);
                        slen -= mlen;
                        dhpp = dhpp->dh_next;
                        off = 0;
                }
                /*
                 * synchonize with other faulting threads and wait till safe
                 * devmap_softlock_enter might return due to signal in cv_wait
                 *
                 * devmap_softlock_enter has to be called outside of while loop
                 * to prevent a deadlock if len spans over multiple dhps.
                 * dh_softlock is based on device instance and if multiple dhps
                 * use the same device instance, the second dhp's LOCK call
                 * will hang waiting on the first to complete.
                 * devmap_setup verifies that slocks in a dhp_chain are same.
                 * RFE: this deadlock only hold true for F_SOFTLOCK. For
                 *      F_INVAL/F_PROT, since we now allow multiple in parallel,
                 *      we could have done the softlock_enter inside the loop
                 *      and supported multi-dhp mappings with dissimilar devices
                 */
                if (err = devmap_softlock_enter(slock, slpage, type))
                        return (FC_MAKE_ERR(err));
        }

        /* reset 'maddr' to the start addr of the range of fault. */
        maddr = addr;

        /* calculate the offset corresponds to 'addr' in the first dhp. */
        off = (ulong_t)(addr - dhp->dh_uvaddr);

        /*
         * The fault length may span over multiple dhps.
         * Loop until the total length is satisfied.
         */
        while (len != 0) {
                size_t llen;
                size_t mlen;
                caddr_t laddr;

                /*
                 * mlen is the smaller of 'len' and the length
                 * from addr to the end of mapping defined by dhp.
                 */
                mlen = MIN(len, (dhp->dh_len - off));

                HOLD_DHP_LOCK(dhp);
                /*
                 * Pass the extended length and address to devmap_access
                 * if large pagesize is used for loading address translations.
                 */
                if ((sdp->pageprot == 0) &&
                    (dhp->dh_flags & DEVMAP_FLAG_LARGE)) {
                        devmap_get_large_pgsize(dhp, mlen, maddr,
                            &llen, &laddr);
                        ASSERT(maddr == addr || laddr == maddr);
                } else {
                        llen = mlen;
                        laddr = maddr;
                }

                if (dhp->dh_callbackops.devmap_access != NULL) {
                        offset_t aoff;

                        aoff = sdp->offset + (offset_t)(laddr - seg->s_base);

                        /*
                         * call driver's devmap_access entry point which will
                         * call devmap_load/contextmgmt to load the translations
                         *
                         * We drop the dhp_lock before calling access so
                         * drivers can call devmap_*_remap within access
                         */
                        RELE_DHP_LOCK(dhp);

                        err = (*dhp->dh_callbackops.devmap_access)(
                            dhp, (void *)dhp->dh_pvtp, aoff, llen, type, rw);
                } else {
                        /*
                         * If no devmap_access entry point, then load mappings
                         * hold dhp_lock across faultpages if REMAP
                         */
                        err = segdev_faultpages(hat, seg, laddr, llen,
                            type, rw, dhp);
                        err_is_faultcode = 1;
                        RELE_DHP_LOCK(dhp);
                }

                if (err) {
                        if ((type == F_SOFTLOCK) && (maddr > addr)) {
                                /*
                                 * If not first dhp, use
                                 * segdev_fault(F_SOFTUNLOCK) for prior dhps
                                 * While this is recursion, it is incorrect to
                                 * call just segdev_softunlock
                                 * if we are using either large pages
                                 * or devmap_access. It will be more right
                                 * to go through the same loop as above
                                 * rather than call segdev_softunlock directly
                                 * It will use the right lenghths as well as
                                 * call into the driver devmap_access routines.
                                 */
                                size_t done = (size_t)(maddr - addr);
                                (void) segdev_fault(hat, seg, addr, done,
                                    F_SOFTUNLOCK, S_OTHER);
                                /*
                                 * reduce slpage by number of pages
                                 * released by segdev_softunlock
                                 */
                                ASSERT(slpage >= btopr(done));
                                devmap_softlock_exit(slock,
                                    slpage - btopr(done), type);
                        } else {
                                devmap_softlock_exit(slock, slpage, type);
                        }


                        /*
                         * Segdev_faultpages() already returns a faultcode,
                         * hence, result from segdev_faultpages() should be
                         * returned directly.
                         */
                        if (err_is_faultcode)
                                return (err);
                        return (FC_MAKE_ERR(err));
                }

                maddr += mlen;
                ASSERT(len >= mlen);
                len -= mlen;
                dhp = dhp->dh_next;
                off = 0;

                ASSERT(!dhp || len == 0 || maddr == dhp->dh_uvaddr);
        }
        /*
         * release the softlock count at end of fault
         * For F_SOFTLOCk this is done in the later F_SOFTUNLOCK
         */
        if ((type == F_INVAL) || (type == F_PROT))
                devmap_softlock_exit(slock, slpage, type);
        return (0);
}

/*
 * segdev_faultpages
 *
 * Used to fault in seg_dev segment pages. Called by segdev_fault or devmap_load
 * This routine assumes that the callers makes sure that the fields
 * in dhp used below are not changed due to remap during this call.
 * Caller does HOLD_DHP_LOCK if neeed
 * This routine returns a faultcode_t as a return value for segdev_fault.
 */
static faultcode_t
segdev_faultpages(
        struct hat *hat,                /* the hat */
        struct seg *seg,                /* the seg_dev of interest */
        caddr_t addr,                   /* the address of the fault */
        size_t len,                     /* the length of the range */
        enum fault_type type,           /* type of fault */
        enum seg_rw rw,                 /* type of access at fault */
        devmap_handle_t *dhp)           /* devmap handle */
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        register caddr_t a;
        struct vpage *vpage;
        struct ddi_umem_cookie *kpmem_cookie = NULL;
        int err;

        DEBUGF(5, (CE_CONT, "segdev_faultpages: "
            "dhp %p seg %p addr %p len %lx\n",
            (void *)dhp, (void *)seg, (void *)addr, len));

        /*
         * The seg_dev driver does not implement copy-on-write,
         * and always loads translations with maximal allowed permissions
         * but we got an fault trying to access the device.
         * Servicing the fault is not going to result in any better result
         * XXX: If we want to allow devmap_access to handle F_PROT calls,
         * This code should be removed and let the normal fault handling
         * take care of finding the error
         */
        if (type == F_PROT) {
                return (FC_PROT);
        }

        if (type == F_SOFTUNLOCK) {
                segdev_softunlock(hat, seg, addr, len, rw);
                return (0);
        }

        /*
         * For kernel pageable memory, fault/lock segkp pages
         * We hold this until the completion of this
         * fault (INVAL/PROT) or till unlock (SOFTLOCK).
         */
        if ((dhp != NULL) && dhp_is_kpmem(dhp)) {
                kpmem_cookie = (struct ddi_umem_cookie *)dhp->dh_cookie;
                if (err = acquire_kpmem_lock(kpmem_cookie, btopr(len)))
                        return (err);
        }

        /*
         * If we have the same protections for the entire segment,
         * insure that the access being attempted is legitimate.
         */
        rw_enter(&sdp->lock, RW_READER);
        if (sdp->pageprot == 0) {
                uint_t protchk;

                switch (rw) {
                case S_READ:
                        protchk = PROT_READ;
                        break;
                case S_WRITE:
                        protchk = PROT_WRITE;
                        break;
                case S_EXEC:
                        protchk = PROT_EXEC;
                        break;
                case S_OTHER:
                default:
                        protchk = PROT_READ | PROT_WRITE | PROT_EXEC;
                        break;
                }

                if ((sdp->prot & protchk) == 0) {
                        rw_exit(&sdp->lock);
                        /* undo kpmem locking */
                        if (kpmem_cookie != NULL) {
                                release_kpmem_lock(kpmem_cookie, btopr(len));
                        }
                        return (FC_PROT);       /* illegal access type */
                }
        }

        /*
         * we do a single hat_devload for the range if
         *   - devmap framework (dhp is not NULL),
         *   - pageprot == 0, i.e., no per-page protection set and
         *   - is device pages, irrespective of whether we are using large pages
         */
        if ((sdp->pageprot == 0) && (dhp != NULL) && dhp_is_devmem(dhp)) {
                pfn_t pfnum;
                uint_t hat_flags;

                if (dhp->dh_flags & DEVMAP_MAPPING_INVALID) {
                        rw_exit(&sdp->lock);
                        return (FC_NOMAP);
                }

                if (type == F_SOFTLOCK) {
                        mutex_enter(&freemem_lock);
                        sdp->softlockcnt += btopr(len);
                        mutex_exit(&freemem_lock);
                }

                hat_flags = ((type == F_SOFTLOCK) ? HAT_LOAD_LOCK : HAT_LOAD);
                pfnum = dhp->dh_pfn + btop((uintptr_t)(addr - dhp->dh_uvaddr));
                ASSERT(!pf_is_memory(pfnum));

                hat_devload(hat, addr, len, pfnum, sdp->prot | dhp->dh_hat_attr,
                    hat_flags | sdp->hat_flags);
                rw_exit(&sdp->lock);
                return (0);
        }

        /* Handle cases where we have to loop through fault handling per-page */

        if (sdp->vpage == NULL)
                vpage = NULL;
        else
                vpage = &sdp->vpage[seg_page(seg, addr)];

        /* loop over the address range handling each fault */
        for (a = addr; a < addr + len; a += PAGESIZE) {
                if (err = segdev_faultpage(hat, seg, a, vpage, type, rw, dhp)) {
                        break;
                }
                if (vpage != NULL)
                        vpage++;
        }
        rw_exit(&sdp->lock);
        if (err && (type == F_SOFTLOCK)) { /* error handling for F_SOFTLOCK */
                size_t done = (size_t)(a - addr); /* pages fault successfully */
                if (done > 0) {
                        /* use softunlock for those pages */
                        segdev_softunlock(hat, seg, addr, done, S_OTHER);
                }
                if (kpmem_cookie != NULL) {
                        /* release kpmem lock for rest of pages */
                        ASSERT(len >= done);
                        release_kpmem_lock(kpmem_cookie, btopr(len - done));
                }
        } else if ((kpmem_cookie != NULL) && (type != F_SOFTLOCK)) {
                /* for non-SOFTLOCK cases, release kpmem */
                release_kpmem_lock(kpmem_cookie, btopr(len));
        }
        return (err);
}

/*
 * Asynchronous page fault.  We simply do nothing since this
 * entry point is not supposed to load up the translation.
 */
/*ARGSUSED*/
static faultcode_t
segdev_faulta(struct seg *seg, caddr_t addr)
{
        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return (0);
}

static int
segdev_setprot(struct seg *seg, caddr_t addr, size_t len, uint_t prot)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        register devmap_handle_t *dhp;
        register struct vpage *vp, *evp;
        devmap_handle_t *dhp_head = (devmap_handle_t *)sdp->devmap_data;
        ulong_t off;
        size_t mlen, sz;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        if ((sz = sdp->softlockcnt) > 0 && dhp_head != NULL) {
                /*
                 * Fail the setprot if pages are SOFTLOCKed through this
                 * mapping.
                 * Softlockcnt is protected from change by the as read lock.
                 */
                DEBUGF(1, (CE_CONT, "segdev_setprot: softlockcnt %ld\n", sz));
                return (EAGAIN);
        }

        if (dhp_head != NULL) {
                if ((dhp = devmap_find_handle(dhp_head, addr)) == NULL)
                        return (EINVAL);

                /*
                 * check if violate maxprot.
                 */
                off = (ulong_t)(addr - dhp->dh_uvaddr);
                mlen  = len;
                while (dhp) {
                        if ((dhp->dh_maxprot & prot) != prot)
                                return (EACCES);        /* violated maxprot */

                        if (mlen > (dhp->dh_len - off)) {
                                mlen -= dhp->dh_len - off;
                                dhp = dhp->dh_next;
                                off = 0;
                        } else
                                break;
                }
        } else {
                if ((sdp->maxprot & prot) != prot)
                        return (EACCES);
        }

        rw_enter(&sdp->lock, RW_WRITER);
        if (addr == seg->s_base && len == seg->s_size && sdp->pageprot == 0) {
                if (sdp->prot == prot) {
                        rw_exit(&sdp->lock);
                        return (0);                     /* all done */
                }
                sdp->prot = (uchar_t)prot;
        } else {
                sdp->pageprot = 1;
                if (sdp->vpage == NULL) {
                        /*
                         * First time through setting per page permissions,
                         * initialize all the vpage structures to prot
                         */
                        sdp->vpage = kmem_zalloc(vpgtob(seg_pages(seg)),
                            KM_SLEEP);
                        evp = &sdp->vpage[seg_pages(seg)];
                        for (vp = sdp->vpage; vp < evp; vp++)
                                VPP_SETPROT(vp, sdp->prot);
                }
                /*
                 * Now go change the needed vpages protections.
                 */
                evp = &sdp->vpage[seg_page(seg, addr + len)];
                for (vp = &sdp->vpage[seg_page(seg, addr)]; vp < evp; vp++)
                        VPP_SETPROT(vp, prot);
        }
        rw_exit(&sdp->lock);

        if (dhp_head != NULL) {
                devmap_handle_t *tdhp;
                /*
                 * If large page size was used in hat_devload(),
                 * the same page size must be used in hat_unload().
                 */
                dhp = tdhp = devmap_find_handle(dhp_head, addr);
                while (tdhp != NULL) {
                        if (tdhp->dh_flags & DEVMAP_FLAG_LARGE) {
                                break;
                        }
                        tdhp = tdhp->dh_next;
                }
                if (tdhp) {
                        size_t slen = len;
                        size_t mlen;
                        size_t soff;

                        soff = (ulong_t)(addr - dhp->dh_uvaddr);
                        while (slen != 0) {
                                mlen = MIN(slen, (dhp->dh_len - soff));
                                hat_unload(seg->s_as->a_hat, dhp->dh_uvaddr,
                                    dhp->dh_len, HAT_UNLOAD);
                                dhp = dhp->dh_next;
                                ASSERT(slen >= mlen);
                                slen -= mlen;
                                soff = 0;
                        }
                        return (0);
                }
        }

        if ((prot & ~PROT_USER) == PROT_NONE) {
                hat_unload(seg->s_as->a_hat, addr, len, HAT_UNLOAD);
        } else {
                /*
                 * RFE: the segment should keep track of all attributes
                 * allowing us to remove the deprecated hat_chgprot
                 * and use hat_chgattr.
                 */
                hat_chgprot(seg->s_as->a_hat, addr, len, prot);
        }

        return (0);
}

static int
segdev_checkprot(struct seg *seg, caddr_t addr, size_t len, uint_t prot)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        struct vpage *vp, *evp;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        /*
         * If segment protection can be used, simply check against them
         */
        rw_enter(&sdp->lock, RW_READER);
        if (sdp->pageprot == 0) {
                register int err;

                err = ((sdp->prot & prot) != prot) ? EACCES : 0;
                rw_exit(&sdp->lock);
                return (err);
        }

        /*
         * Have to check down to the vpage level
         */
        evp = &sdp->vpage[seg_page(seg, addr + len)];
        for (vp = &sdp->vpage[seg_page(seg, addr)]; vp < evp; vp++) {
                if ((VPP_PROT(vp) & prot) != prot) {
                        rw_exit(&sdp->lock);
                        return (EACCES);
                }
        }
        rw_exit(&sdp->lock);
        return (0);
}

static int
segdev_getprot(struct seg *seg, caddr_t addr, size_t len, uint_t *protv)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        size_t pgno;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        pgno = seg_page(seg, addr + len) - seg_page(seg, addr) + 1;
        if (pgno != 0) {
                rw_enter(&sdp->lock, RW_READER);
                if (sdp->pageprot == 0) {
                        do {
                                protv[--pgno] = sdp->prot;
                        } while (pgno != 0);
                } else {
                        size_t pgoff = seg_page(seg, addr);

                        do {
                                pgno--;
                                protv[pgno] =
                                    VPP_PROT(&sdp->vpage[pgno + pgoff]);
                        } while (pgno != 0);
                }
                rw_exit(&sdp->lock);
        }
        return (0);
}

static uoff_t
segdev_getoffset(register struct seg *seg, caddr_t addr)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return ((uoff_t)sdp->offset + (addr - seg->s_base));
}

/*ARGSUSED*/
static int
segdev_gettype(register struct seg *seg, caddr_t addr)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return (sdp->type);
}


/*ARGSUSED*/
static int
segdev_getvp(register struct seg *seg, caddr_t addr, struct vnode **vpp)
{
        register struct segdev_data *sdp = (struct segdev_data *)seg->s_data;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        /*
         * Note that this vp is the common_vp of the device, where the
         * pages are hung ..
         */
        *vpp = VTOCVP(sdp->vp);

        return (0);
}

static void
segdev_badop(void)
{
        panic("segdev_badop");
        /*NOTREACHED*/
}

/*
 * segdev pages are not in the cache, and thus can't really be controlled.
 * Hence, syncs are simply always successful.
 */
/*ARGSUSED*/
static int
segdev_sync(struct seg *seg, caddr_t addr, size_t len, int attr, uint_t flags)
{
        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return (0);
}

/*
 * segdev pages are always "in core".
 */
/*ARGSUSED*/
static size_t
segdev_incore(struct seg *seg, caddr_t addr, size_t len, char *vec)
{
        size_t v = 0;

        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        for (len = (len + PAGEOFFSET) & PAGEMASK; len; len -= PAGESIZE,
            v += PAGESIZE)
                *vec++ = 1;
        return (v);
}

/*
 * segdev pages are not in the cache, and thus can't really be controlled.
 * Hence, locks are simply always successful.
 */
/*ARGSUSED*/
static int
segdev_lockop(struct seg *seg, caddr_t addr,
    size_t len, int attr, int op, ulong_t *lockmap, size_t pos)
{
        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return (0);
}

/*
 * segdev pages are not in the cache, and thus can't really be controlled.
 * Hence, advise is simply always successful.
 */
/*ARGSUSED*/
static int
segdev_advise(struct seg *seg, caddr_t addr, size_t len, uint_t behav)
{
        ASSERT(seg->s_as && AS_LOCK_HELD(seg->s_as));

        return (0);
}

/*
 * ddi_segmap_setup:    Used by drivers who wish specify mapping attributes
 *                      for a segment.  Called from a drivers segmap(9E)
 *                      routine.
 */
/*ARGSUSED*/
int
ddi_segmap_setup(dev_t dev, off_t offset, struct as *as, caddr_t *addrp,
    off_t len, uint_t prot, uint_t maxprot, uint_t flags, cred_t *cred,
    ddi_device_acc_attr_t *accattrp, uint_t rnumber)
{
        struct segdev_crargs dev_a;
        int (*mapfunc)(dev_t dev, off_t off, int prot);
        uint_t hat_attr;
        pfn_t pfn;
        int     error, i;

        if ((mapfunc = devopsp[getmajor(dev)]->devo_cb_ops->cb_mmap) == nodev)
                return (ENODEV);

        /*
         * Character devices that support the d_mmap
         * interface can only be mmap'ed shared.
         */
        if ((flags & MAP_TYPE) != MAP_SHARED)
                return (EINVAL);

        /*
         * Check that this region is indeed mappable on this platform.
         * Use the mapping function.
         */
        if (ddi_device_mapping_check(dev, accattrp, rnumber, &hat_attr) == -1)
                return (ENXIO);

        /*
         * Check to ensure that the entire range is
         * legal and we are not trying to map in
         * more than the device will let us.
         */
        for (i = 0; i < len; i += PAGESIZE) {
                if (i == 0) {
                        /*
                         * Save the pfn at offset here. This pfn will be
                         * used later to get user address.
                         */
                        if ((pfn = (pfn_t)cdev_mmap(mapfunc, dev, offset,
                            maxprot)) == PFN_INVALID)
                                return (ENXIO);
                } else {
                        if (cdev_mmap(mapfunc, dev, offset + i, maxprot) ==
                            PFN_INVALID)
                                return (ENXIO);
                }
        }

        as_rangelock(as);
        /* Pick an address w/o worrying about any vac alignment constraints. */
        error = choose_addr(as, addrp, len, ptob(pfn), ADDR_NOVACALIGN, flags);
        if (error != 0) {
                as_rangeunlock(as);
                return (error);
        }

        dev_a.mapfunc = mapfunc;
        dev_a.dev = dev;
        dev_a.offset = (offset_t)offset;
        dev_a.type = flags & MAP_TYPE;
        dev_a.prot = (uchar_t)prot;
        dev_a.maxprot = (uchar_t)maxprot;
        dev_a.hat_attr = hat_attr;
        dev_a.hat_flags = 0;
        dev_a.devmap_data = NULL;

        error = as_map(as, *addrp, len, segdev_create, &dev_a);
        as_rangeunlock(as);
        return (error);

}

/*ARGSUSED*/
static int
segdev_pagelock(struct seg *seg, caddr_t addr, size_t len,
    struct page ***ppp, enum lock_type type, enum seg_rw rw)
{
        return (ENOTSUP);
}

/*
 * devmap_device: Used by devmap framework to establish mapping
 *                called by devmap_seup(9F) during map setup time.
 */
/*ARGSUSED*/
static int
devmap_device(devmap_handle_t *dhp, struct as *as, caddr_t *addr,
    offset_t off, size_t len, uint_t flags)
{
        devmap_handle_t *rdhp, *maxdhp;
        struct segdev_crargs dev_a;
        int     err;
        uint_t maxprot = PROT_ALL;
        offset_t offset = 0;
        pfn_t pfn;
        struct devmap_pmem_cookie *pcp;

        DEBUGF(2, (CE_CONT, "devmap_device: dhp %p addr %p off %llx len %lx\n",
            (void *)dhp, (void *)addr, off, len));

        as_rangelock(as);
        if ((flags & MAP_FIXED) == 0) {
                offset_t aligned_off;

                rdhp = maxdhp = dhp;
                while (rdhp != NULL) {
                        maxdhp = (maxdhp->dh_len > rdhp->dh_len) ?
                            maxdhp : rdhp;
                        rdhp = rdhp->dh_next;
                        maxprot |= dhp->dh_maxprot;
                }
                offset = maxdhp->dh_uoff - dhp->dh_uoff;

                /*
                 * Use the dhp that has the
                 * largest len to get user address.
                 */
                /*
                 * If MAPPING_INVALID, cannot use dh_pfn/dh_cvaddr,
                 * use 0 which is as good as any other.
                 */
                if (maxdhp->dh_flags & DEVMAP_MAPPING_INVALID) {
                        aligned_off = 0;
                } else if (dhp_is_devmem(maxdhp)) {
                        aligned_off = (offset_t)ptob(maxdhp->dh_pfn) - offset;
                } else if (dhp_is_pmem(maxdhp)) {
                        pcp = (struct devmap_pmem_cookie *)maxdhp->dh_pcookie;
                        pfn = page_pptonum(
                            pcp->dp_pparray[btop(maxdhp->dh_roff)]);
                        aligned_off = (offset_t)ptob(pfn) - offset;
                } else {
                        aligned_off = (offset_t)(uintptr_t)maxdhp->dh_cvaddr -
                            offset;
                }

                /*
                 * Pick an address aligned to dh_cookie.
                 * for kernel memory/user memory, cookie is cvaddr.
                 * for device memory, cookie is physical address.
                 */
                map_addr(addr, len, aligned_off, 1, flags);
                if (*addr == NULL) {
                        as_rangeunlock(as);
                        return (ENOMEM);
                }
        } else {
                /*
                 * User-specified address; blow away any previous mappings.
                 */
                (void) as_unmap(as, *addr, len);
        }

        dev_a.mapfunc = NULL;
        dev_a.dev = dhp->dh_dev;
        dev_a.type = flags & MAP_TYPE;
        dev_a.offset = off;
        /*
         * sdp->maxprot has the least restrict protection of all dhps.
         */
        dev_a.maxprot = maxprot;
        dev_a.prot = dhp->dh_prot;
        /*
         * devmap uses dhp->dh_hat_attr for hat.
         */
        dev_a.hat_flags = 0;
        dev_a.hat_attr = 0;
        dev_a.devmap_data = (void *)dhp;

        err = as_map(as, *addr, len, segdev_create, &dev_a);
        as_rangeunlock(as);
        return (err);
}

int
devmap_do_ctxmgt(devmap_cookie_t dhc, void *pvtp, offset_t off, size_t len,
    uint_t type, uint_t rw, int (*ctxmgt)(devmap_cookie_t, void *, offset_t,
    size_t, uint_t, uint_t))
{
        register devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        struct devmap_ctx *devctx;
        int do_timeout = 0;
        int ret;


        DEBUGF(7, (CE_CONT, "devmap_do_ctxmgt: dhp %p off %llx len %lx\n",
            (void *)dhp, off, len));

        if (ctxmgt == NULL)
                return (FC_HWERR);

        devctx = dhp->dh_ctx;

        /*
         * If we are on an MP system with more than one cpu running
         * and if a thread on some CPU already has the context, wait
         * for it to finish if there is a hysteresis timeout.
         *
         * We call cv_wait() instead of cv_wait_sig() because
         * it does not matter much if it returned due to a signal
         * or due to a cv_signal() or cv_broadcast().  In either event
         * we need to complete the mapping otherwise the processes
         * will die with a SEGV.
         */
        if ((dhp->dh_timeout_length > 0) && (ncpus > 1)) {
                do_timeout = 1;
                mutex_enter(&devctx->lock);
                while (devctx->oncpu)
                        cv_wait(&devctx->cv, &devctx->lock);
                devctx->oncpu = 1;
                mutex_exit(&devctx->lock);
        }

        /*
         * Call the contextmgt callback so that the driver can handle
         * the fault.
         */
        ret = (*ctxmgt)(dhp, dhp->dh_pvtp, off, len, type, rw);

        /*
         * If devmap_access() returned -1, then there was a hardware
         * error so we need to convert the return value to something
         * that trap() will understand.  Otherwise, the return value
         * is already a fault code generated by devmap_unload()
         * or devmap_load().
         */
        if (ret) {
                DEBUGF(1, (CE_CONT, "devmap_do_ctxmgt: ret %x dhp %p\n",
                    ret, (void *)dhp));
                if (devctx->oncpu) {
                        mutex_enter(&devctx->lock);
                        devctx->oncpu = 0;
                        cv_signal(&devctx->cv);
                        mutex_exit(&devctx->lock);
                }
                return (FC_HWERR);
        }

        /*
         * Setup the timeout if we need to
         */
        if (do_timeout) {
                mutex_enter(&devctx->lock);
                if (dhp->dh_timeout_length > 0) {
                        devctx->timeout = timeout(devmap_ctxto,
                            devctx, dhp->dh_timeout_length);
                } else {
                        /*
                         * We don't want to wait so set oncpu to
                         * 0 and wake up anyone waiting.
                         */
                        devctx->oncpu = 0;
                        cv_signal(&devctx->cv);
                }
                mutex_exit(&devctx->lock);
        }

        return (DDI_SUCCESS);
}

/*
 *                                       end of mapping
 *                    poff   fault_offset         |
 *            base     |        |                 |
 *              |      |        |                 |
 *              V      V        V                 V
 *  +-----------+---------------+-------+---------+-------+
 *              ^               ^       ^         ^
 *              |<--- offset--->|<-len->|         |
 *              |<--- dh_len(size of mapping) --->|
 *                     |<--  pg -->|
 *                              -->|rlen|<--
 */
static ulong_t
devmap_roundup(devmap_handle_t *dhp, ulong_t offset, size_t len,
    ulong_t *opfn, ulong_t *pagesize)
{
        register int level;
        ulong_t pg;
        ulong_t poff;
        ulong_t base;
        caddr_t uvaddr;
        long rlen;

        DEBUGF(2, (CE_CONT, "devmap_roundup: dhp %p off %lx len %lx\n",
            (void *)dhp, offset, len));

        /*
         * get the max. pagesize that is aligned within the range
         * <dh_pfn, dh_pfn+offset>.
         *
         * The calculations below use physical address to ddetermine
         * the page size to use. The same calculations can use the
         * virtual address to determine the page size.
         */
        base = (ulong_t)ptob(dhp->dh_pfn);
        for (level = dhp->dh_mmulevel; level >= 0; level--) {
                pg = page_get_pagesize(level);
                poff = ((base + offset) & ~(pg - 1));
                uvaddr = dhp->dh_uvaddr + (poff - base);
                if ((poff >= base) &&
                    ((poff + pg) <= (base + dhp->dh_len)) &&
                    VA_PA_ALIGNED((uintptr_t)uvaddr, poff, pg))
                        break;
        }

        DEBUGF(2, (CE_CONT, "devmap_roundup: base %lx poff %lx pfn %lx\n",
            base, poff, dhp->dh_pfn));

        ASSERT(VA_PA_ALIGNED((uintptr_t)uvaddr, poff, pg));
        ASSERT(level >= 0);

        *pagesize = pg;
        *opfn = dhp->dh_pfn + btop(poff - base);

        rlen = len + offset - (poff - base + pg);

        ASSERT(rlen < (long)len);

        DEBUGF(1, (CE_CONT, "devmap_roundup: dhp %p "
            "level %x rlen %lx psize %lx opfn %lx\n",
            (void *)dhp, level, rlen, *pagesize, *opfn));

        return ((ulong_t)((rlen > 0) ? rlen : 0));
}

/*
 * find the dhp that contains addr.
 */
static devmap_handle_t *
devmap_find_handle(devmap_handle_t *dhp_head, caddr_t addr)
{
        devmap_handle_t *dhp;

        dhp = dhp_head;
        while (dhp) {
                if (addr >= dhp->dh_uvaddr &&
                    addr < (dhp->dh_uvaddr + dhp->dh_len))
                        return (dhp);
                dhp = dhp->dh_next;
        }

        return ((devmap_handle_t *)NULL);
}

/*
 * devmap_unload:
 *                      Marks a segdev segment or pages if offset->offset+len
 *                      is not the entire segment as intercept and unloads the
 *                      pages in the range offset -> offset+len.
 */
int
devmap_unload(devmap_cookie_t dhc, offset_t offset, size_t len)
{
        register devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        caddr_t addr;
        ulong_t size;
        ssize_t soff;

        DEBUGF(7, (CE_CONT, "devmap_unload: dhp %p offset %llx len %lx\n",
            (void *)dhp, offset, len));

        soff = (ssize_t)(offset - dhp->dh_uoff);
        soff = round_down_p2(soff, PAGESIZE);
        if (soff < 0 || soff >= dhp->dh_len)
                return (FC_MAKE_ERR(EINVAL));

        /*
         * Address and size must be page aligned.  Len is set to the
         * number of bytes in the number of pages that are required to
         * support len.  Offset is set to the byte offset of the first byte
         * of the page that contains offset.
         */
        len = round_up_p2(len, PAGESIZE);

        /*
         * If len is == 0, then calculate the size by getting
         * the number of bytes from offset to the end of the segment.
         */
        if (len == 0)
                size = dhp->dh_len - soff;
        else {
                size = len;
                if ((soff + size) > dhp->dh_len)
                        return (FC_MAKE_ERR(EINVAL));
        }

        /*
         * The address is offset bytes from the base address of
         * the dhp.
         */
        addr = (caddr_t)(soff + dhp->dh_uvaddr);

        /*
         * If large page size was used in hat_devload(),
         * the same page size must be used in hat_unload().
         */
        if (dhp->dh_flags & DEVMAP_FLAG_LARGE) {
                hat_unload(dhp->dh_seg->s_as->a_hat, dhp->dh_uvaddr,
                    dhp->dh_len, HAT_UNLOAD|HAT_UNLOAD_OTHER);
        } else {
                hat_unload(dhp->dh_seg->s_as->a_hat,  addr, size,
                    HAT_UNLOAD|HAT_UNLOAD_OTHER);
        }

        return (0);
}

/*
 * calculates the optimal page size that will be used for hat_devload().
 */
static void
devmap_get_large_pgsize(devmap_handle_t *dhp, size_t len, caddr_t addr,
    size_t *llen, caddr_t *laddr)
{
        ulong_t off;
        ulong_t pfn;
        ulong_t pgsize;
        uint_t first = 1;

        /*
         * RFE - Code only supports large page mappings for devmem
         * This code could be changed in future if we want to support
         * large page mappings for kernel exported memory.
         */
        ASSERT(dhp_is_devmem(dhp));
        ASSERT(!(dhp->dh_flags & DEVMAP_MAPPING_INVALID));

        *llen = 0;
        off = (ulong_t)(addr - dhp->dh_uvaddr);
        while ((long)len > 0) {
                /*
                 * get the optimal pfn to minimize address translations.
                 * devmap_roundup() returns residue bytes for next round
                 * calculations.
                 */
                len = devmap_roundup(dhp, off, len, &pfn, &pgsize);

                if (first) {
                        *laddr = dhp->dh_uvaddr + ptob(pfn - dhp->dh_pfn);
                        first = 0;
                }

                *llen += pgsize;
                off = ptob(pfn - dhp->dh_pfn) + pgsize;
        }
        /* Large page mapping len/addr cover more range than original fault */
        ASSERT(*llen >= len && *laddr <= addr);
        ASSERT((*laddr + *llen) >= (addr + len));
}

/*
 * Initialize the devmap_softlock structure.
 */
static struct devmap_softlock *
devmap_softlock_init(dev_t dev, ulong_t id)
{
        struct devmap_softlock *slock;
        struct devmap_softlock *tmp;

        tmp = kmem_zalloc(sizeof (struct devmap_softlock), KM_SLEEP);
        mutex_enter(&devmap_slock);

        for (slock = devmap_slist; slock != NULL; slock = slock->next)
                if ((slock->dev == dev) && (slock->id == id))
                        break;

        if (slock == NULL) {
                slock = tmp;
                slock->dev = dev;
                slock->id = id;
                mutex_init(&slock->lock, NULL, MUTEX_DEFAULT, NULL);
                cv_init(&slock->cv, NULL, CV_DEFAULT, NULL);
                slock->next = devmap_slist;
                devmap_slist = slock;
        } else
                kmem_free(tmp, sizeof (struct devmap_softlock));

        mutex_enter(&slock->lock);
        slock->refcnt++;
        mutex_exit(&slock->lock);
        mutex_exit(&devmap_slock);

        return (slock);
}

/*
 * Wake up processes that sleep on softlocked.
 * Free dh_softlock if refcnt is 0.
 */
static void
devmap_softlock_rele(devmap_handle_t *dhp)
{
        struct devmap_softlock *slock = dhp->dh_softlock;
        struct devmap_softlock *tmp;
        struct devmap_softlock *parent;

        mutex_enter(&devmap_slock);
        mutex_enter(&slock->lock);

        ASSERT(slock->refcnt > 0);

        slock->refcnt--;

        /*
         * If no one is using the device, free up the slock data.
         */
        if (slock->refcnt == 0) {
                slock->softlocked = 0;
                cv_signal(&slock->cv);

                if (devmap_slist == slock)
                        devmap_slist = slock->next;
                else {
                        parent = devmap_slist;
                        for (tmp = devmap_slist->next; tmp != NULL;
                            tmp = tmp->next) {
                                if (tmp == slock) {
                                        parent->next = tmp->next;
                                        break;
                                }
                                parent = tmp;
                        }
                }
                mutex_exit(&slock->lock);
                mutex_destroy(&slock->lock);
                cv_destroy(&slock->cv);
                kmem_free(slock, sizeof (struct devmap_softlock));
        } else
                mutex_exit(&slock->lock);

        mutex_exit(&devmap_slock);
}

/*
 * Wake up processes that sleep on dh_ctx->locked.
 * Free dh_ctx if refcnt is 0.
 */
static void
devmap_ctx_rele(devmap_handle_t *dhp)
{
        struct devmap_ctx *devctx = dhp->dh_ctx;
        struct devmap_ctx *tmp;
        struct devmap_ctx *parent;
        timeout_id_t tid;

        mutex_enter(&devmapctx_lock);
        mutex_enter(&devctx->lock);

        ASSERT(devctx->refcnt > 0);

        devctx->refcnt--;

        /*
         * If no one is using the device, free up the devctx data.
         */
        if (devctx->refcnt == 0) {
                /*
                 * Untimeout any threads using this mapping as they are about
                 * to go away.
                 */
                if (devctx->timeout != 0) {
                        tid = devctx->timeout;
                        mutex_exit(&devctx->lock);
                        (void) untimeout(tid);
                        mutex_enter(&devctx->lock);
                }

                devctx->oncpu = 0;
                cv_signal(&devctx->cv);

                if (devmapctx_list == devctx)
                        devmapctx_list = devctx->next;
                else {
                        parent = devmapctx_list;
                        for (tmp = devmapctx_list->next; tmp != NULL;
                            tmp = tmp->next) {
                                if (tmp == devctx) {
                                        parent->next = tmp->next;
                                        break;
                                }
                                parent = tmp;
                        }
                }
                mutex_exit(&devctx->lock);
                mutex_destroy(&devctx->lock);
                cv_destroy(&devctx->cv);
                kmem_free(devctx, sizeof (struct devmap_ctx));
        } else
                mutex_exit(&devctx->lock);

        mutex_exit(&devmapctx_lock);
}

/*
 * devmap_load:
 *                      Marks a segdev segment or pages if offset->offset+len
 *                      is not the entire segment as nointercept and faults in
 *                      the pages in the range offset -> offset+len.
 */
int
devmap_load(devmap_cookie_t dhc, offset_t offset, size_t len, uint_t type,
    uint_t rw)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        struct as *asp = dhp->dh_seg->s_as;
        caddr_t addr;
        ulong_t size;
        ssize_t soff;   /* offset from the beginning of the segment */
        int rc;

        DEBUGF(7, (CE_CONT, "devmap_load: dhp %p offset %llx len %lx\n",
            (void *)dhp, offset, len));

        /*
         *      Hat layer only supports devload to process' context for which
         *      the as lock is held. Verify here and return error if drivers
         *      inadvertently call devmap_load on a wrong devmap handle.
         */
        if ((asp != &kas) && !AS_LOCK_HELD(asp))
                return (FC_MAKE_ERR(EINVAL));

        soff = (ssize_t)(offset - dhp->dh_uoff);
        soff = round_down_p2(soff, PAGESIZE);
        if (soff < 0 || soff >= dhp->dh_len)
                return (FC_MAKE_ERR(EINVAL));

        /*
         * Address and size must be page aligned.  Len is set to the
         * number of bytes in the number of pages that are required to
         * support len.  Offset is set to the byte offset of the first byte
         * of the page that contains offset.
         */
        len = round_up_p2(len, PAGESIZE);

        /*
         * If len == 0, then calculate the size by getting
         * the number of bytes from offset to the end of the segment.
         */
        if (len == 0)
                size = dhp->dh_len - soff;
        else {
                size = len;
                if ((soff + size) > dhp->dh_len)
                        return (FC_MAKE_ERR(EINVAL));
        }

        /*
         * The address is offset bytes from the base address of
         * the segment.
         */
        addr = (caddr_t)(soff + dhp->dh_uvaddr);

        HOLD_DHP_LOCK(dhp);
        rc = segdev_faultpages(asp->a_hat,
            dhp->dh_seg, addr, size, type, rw, dhp);
        RELE_DHP_LOCK(dhp);
        return (rc);
}

int
devmap_setup(dev_t dev, offset_t off, struct as *as, caddr_t *addrp,
    size_t len, uint_t prot, uint_t maxprot, uint_t flags, struct cred *cred)
{
        register devmap_handle_t *dhp;
        int (*devmap)(dev_t, devmap_cookie_t, offset_t, size_t,
            size_t *, uint_t);
        int (*mmap)(dev_t, off_t, int);
        struct devmap_callback_ctl *callbackops;
        devmap_handle_t *dhp_head = NULL;
        devmap_handle_t *dhp_prev = NULL;
        devmap_handle_t *dhp_curr;
        caddr_t addr;
        int map_flag;
        int ret;
        ulong_t total_len;
        size_t map_len;
        size_t resid_len = len;
        offset_t map_off = off;
        struct devmap_softlock *slock = NULL;


        DEBUGF(3, (CE_CONT, "devmap_setup: off %llx len %lx\n",
            off, len));

        devmap = devopsp[getmajor(dev)]->devo_cb_ops->cb_devmap;
        mmap = devopsp[getmajor(dev)]->devo_cb_ops->cb_mmap;

        /*
         * driver must provide devmap(9E) entry point in cb_ops to use the
         * devmap framework.
         */
        if (devmap == NULL || devmap == nulldev || devmap == nodev)
                return (EINVAL);

        /*
         * To protect from an inadvertent entry because the devmap entry point
         * is not NULL, return error if D_DEVMAP bit is not set in cb_flag and
         * mmap is NULL.
         */
        map_flag = devopsp[getmajor(dev)]->devo_cb_ops->cb_flag;
        if ((map_flag & D_DEVMAP) == 0 && (mmap == NULL || mmap == nulldev))
                return (EINVAL);

        /*
         * devmap allows mmap(2) to map multiple registers.
         * one devmap_handle is created for each register mapped.
         */
        for (total_len = 0; total_len < len; total_len += map_len) {
                dhp = kmem_zalloc(sizeof (devmap_handle_t), KM_SLEEP);

                if (dhp_prev != NULL)
                        dhp_prev->dh_next = dhp;
                else
                        dhp_head = dhp;
                dhp_prev = dhp;

                dhp->dh_prot = prot;
                dhp->dh_orig_maxprot = dhp->dh_maxprot = maxprot;
                dhp->dh_dev = dev;
                dhp->dh_timeout_length = CTX_TIMEOUT_VALUE;
                dhp->dh_uoff = map_off;

                /*
                 * Get mapping specific info from
                 * the driver, such as rnumber, roff, len, callbackops,
                 * accattrp and, if the mapping is for kernel memory,
                 * ddi_umem_cookie.
                 */
                if ((ret = cdev_devmap(dev, dhp, map_off,
                    resid_len, &map_len, get_udatamodel())) != 0) {
                        free_devmap_handle(dhp_head);
                        return (ENXIO);
                }

                if (map_len & PAGEOFFSET) {
                        free_devmap_handle(dhp_head);
                        return (EINVAL);
                }

                callbackops = &dhp->dh_callbackops;

                if ((callbackops->devmap_access == NULL) ||
                    (callbackops->devmap_access == nulldev) ||
                    (callbackops->devmap_access == nodev)) {
                        /*
                         * Normally devmap does not support MAP_PRIVATE unless
                         * the drivers provide a valid devmap_access routine.
                         */
                        if ((flags & MAP_PRIVATE) != 0) {
                                free_devmap_handle(dhp_head);
                                return (EINVAL);
                        }
                } else {
                        /*
                         * Initialize dhp_softlock and dh_ctx if the drivers
                         * provide devmap_access.
                         */
                        dhp->dh_softlock = devmap_softlock_init(dev,
                            (ulong_t)callbackops->devmap_access);
                        dhp->dh_ctx = devmap_ctxinit(dev,
                            (ulong_t)callbackops->devmap_access);

                        /*
                         * segdev_fault can only work when all
                         * dh_softlock in a multi-dhp mapping
                         * are same. see comments in segdev_fault
                         * This code keeps track of the first
                         * dh_softlock allocated in slock and
                         * compares all later allocations and if
                         * not similar, returns an error.
                         */
                        if (slock == NULL)
                                slock = dhp->dh_softlock;
                        if (slock != dhp->dh_softlock) {
                                free_devmap_handle(dhp_head);
                                return (ENOTSUP);
                        }
                }

                map_off += map_len;
                resid_len -= map_len;
        }

        /*
         * get the user virtual address and establish the mapping between
         * uvaddr and device physical address.
         */
        if ((ret = devmap_device(dhp_head, as, addrp, off, len, flags))
            != 0) {
                /*
                 * free devmap handles if error during the mapping.
                 */
                free_devmap_handle(dhp_head);

                return (ret);
        }

        /*
         * call the driver's devmap_map callback to do more after the mapping,
         * such as to allocate driver private data for context management.
         */
        dhp = dhp_head;
        map_off = off;
        addr = *addrp;
        while (dhp != NULL) {
                callbackops = &dhp->dh_callbackops;
                dhp->dh_uvaddr = addr;
                dhp_curr = dhp;
                if (callbackops->devmap_map != NULL) {
                        ret = (*callbackops->devmap_map)((devmap_cookie_t)dhp,
                            dev, flags, map_off,
                            dhp->dh_len, &dhp->dh_pvtp);
                        if (ret != 0) {
                                struct segdev_data *sdp;

                                /*
                                 * call driver's devmap_unmap entry point
                                 * to free driver resources.
                                 */
                                dhp = dhp_head;
                                map_off = off;
                                while (dhp != dhp_curr) {
                                        callbackops = &dhp->dh_callbackops;
                                        if (callbackops->devmap_unmap != NULL) {
                                                (*callbackops->devmap_unmap)(
                                                    dhp, dhp->dh_pvtp,
                                                    map_off, dhp->dh_len,
                                                    NULL, NULL, NULL, NULL);
                                        }
                                        map_off += dhp->dh_len;
                                        dhp = dhp->dh_next;
                                }
                                sdp = dhp_head->dh_seg->s_data;
                                sdp->devmap_data = NULL;
                                free_devmap_handle(dhp_head);
                                return (ENXIO);
                        }
                }
                map_off += dhp->dh_len;
                addr += dhp->dh_len;
                dhp = dhp->dh_next;
        }

        return (0);
}

int
ddi_devmap_segmap(dev_t dev, off_t off, ddi_as_handle_t as, caddr_t *addrp,
    off_t len, uint_t prot, uint_t maxprot, uint_t flags, struct cred *cred)
{
        return (devmap_setup(dev, (offset_t)off, (struct as *)as, addrp,
            (size_t)len, prot, maxprot, flags, cred));
}

/*
 * Called from devmap_devmem_setup/remap to see if can use large pages for
 * this device mapping.
 * Also calculate the max. page size for this mapping.
 * this page size will be used in fault routine for
 * optimal page size calculations.
 */
static void
devmap_devmem_large_page_setup(devmap_handle_t *dhp)
{
        ASSERT(dhp_is_devmem(dhp));
        dhp->dh_mmulevel = 0;

        /*
         * use large page size only if:
         *  1. device memory.
         *  2. mmu supports multiple page sizes,
         *  3. Driver did not disallow it
         *  4. dhp length is at least as big as the large pagesize
         *  5. the uvaddr and pfn are large pagesize aligned
         */
        if (page_num_pagesizes() > 1 &&
            !(dhp->dh_flags & (DEVMAP_USE_PAGESIZE | DEVMAP_MAPPING_INVALID))) {
                ulong_t base;
                int level;

                base = (ulong_t)ptob(dhp->dh_pfn);
                for (level = 1; level < page_num_pagesizes(); level++) {
                        size_t pgsize = page_get_pagesize(level);
                        if ((dhp->dh_len < pgsize) ||
                            (!VA_PA_PGSIZE_ALIGNED((uintptr_t)dhp->dh_uvaddr,
                            base, pgsize))) {
                                break;
                        }
                }
                dhp->dh_mmulevel = level - 1;
        }
        if (dhp->dh_mmulevel > 0) {
                dhp->dh_flags |= DEVMAP_FLAG_LARGE;
        } else {
                dhp->dh_flags &= ~DEVMAP_FLAG_LARGE;
        }
}

/*
 * Called by driver devmap routine to pass device specific info to
 * the framework.    used for device memory mapping only.
 */
int
devmap_devmem_setup(devmap_cookie_t dhc, dev_info_t *dip,
    struct devmap_callback_ctl *callbackops, uint_t rnumber, offset_t roff,
    size_t len, uint_t maxprot, uint_t flags, ddi_device_acc_attr_t *accattrp)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        ddi_acc_handle_t handle;
        ddi_map_req_t mr;
        ddi_acc_hdl_t *hp;
        int err;

        DEBUGF(2, (CE_CONT, "devmap_devmem_setup: dhp %p offset %llx "
            "rnum %d len %lx\n", (void *)dhp, roff, rnumber, len));

        /*
         * First to check if this function has been called for this dhp.
         */
        if (dhp->dh_flags & DEVMAP_SETUP_DONE)
                return (DDI_FAILURE);

        if ((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) != dhp->dh_prot)
                return (DDI_FAILURE);

        if (flags & DEVMAP_MAPPING_INVALID) {
                /*
                 * Don't go up the tree to get pfn if the driver specifies
                 * DEVMAP_MAPPING_INVALID in flags.
                 *
                 * If DEVMAP_MAPPING_INVALID is specified, we have to grant
                 * remap permission.
                 */
                if (!(flags & DEVMAP_ALLOW_REMAP)) {
                        return (DDI_FAILURE);
                }
                dhp->dh_pfn = PFN_INVALID;
        } else {
                handle = impl_acc_hdl_alloc(KM_SLEEP, NULL);
                if (handle == NULL)
                        return (DDI_FAILURE);

                hp = impl_acc_hdl_get(handle);
                hp->ah_vers = VERS_ACCHDL;
                hp->ah_dip = dip;
                hp->ah_rnumber = rnumber;
                hp->ah_offset = roff;
                hp->ah_len = len;
                if (accattrp != NULL)
                        hp->ah_acc = *accattrp;

                mr.map_op = DDI_MO_MAP_LOCKED;
                mr.map_type = DDI_MT_RNUMBER;
                mr.map_obj.rnumber = rnumber;
                mr.map_prot = maxprot & dhp->dh_orig_maxprot;
                mr.map_flags = DDI_MF_DEVICE_MAPPING;
                mr.map_handlep = hp;
                mr.map_vers = DDI_MAP_VERSION;

                /*
                 * up the device tree to get pfn.
                 * The rootnex_map_regspec() routine in nexus drivers has been
                 * modified to return pfn if map_flags is DDI_MF_DEVICE_MAPPING.
                 */
                err = ddi_map(dip, &mr, roff, len, (caddr_t *)&dhp->dh_pfn);
                dhp->dh_hat_attr = hp->ah_hat_flags;
                impl_acc_hdl_free(handle);

                if (err)
                        return (DDI_FAILURE);
        }
        /* Should not be using devmem setup for memory pages */
        ASSERT(!pf_is_memory(dhp->dh_pfn));

        /* Only some of the flags bits are settable by the driver */
        dhp->dh_flags |= (flags & DEVMAP_SETUP_FLAGS);
        dhp->dh_len = ptob(btopr(len));

        dhp->dh_cookie = DEVMAP_DEVMEM_COOKIE;
        dhp->dh_roff = ptob(btop(roff));

        /* setup the dh_mmulevel and DEVMAP_FLAG_LARGE */
        devmap_devmem_large_page_setup(dhp);
        dhp->dh_maxprot = maxprot & dhp->dh_orig_maxprot;
        ASSERT((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) == dhp->dh_prot);


        if (callbackops != NULL) {
                bcopy(callbackops, &dhp->dh_callbackops,
                    sizeof (struct devmap_callback_ctl));
        }

        /*
         * Initialize dh_lock if we want to do remap.
         */
        if (dhp->dh_flags & DEVMAP_ALLOW_REMAP) {
                mutex_init(&dhp->dh_lock, NULL, MUTEX_DEFAULT, NULL);
                dhp->dh_flags |= DEVMAP_LOCK_INITED;
        }

        dhp->dh_flags |= DEVMAP_SETUP_DONE;

        return (DDI_SUCCESS);
}

int
devmap_devmem_remap(devmap_cookie_t dhc, dev_info_t *dip,
    uint_t rnumber, offset_t roff, size_t len, uint_t maxprot,
    uint_t flags, ddi_device_acc_attr_t *accattrp)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        ddi_acc_handle_t handle;
        ddi_map_req_t mr;
        ddi_acc_hdl_t *hp;
        pfn_t   pfn;
        uint_t  hat_flags;
        int     err;

        DEBUGF(2, (CE_CONT, "devmap_devmem_remap: dhp %p offset %llx "
            "rnum %d len %lx\n", (void *)dhp, roff, rnumber, len));

        /*
         * Return failure if setup has not been done or no remap permission
         * has been granted during the setup.
         */
        if ((dhp->dh_flags & DEVMAP_SETUP_DONE) == 0 ||
            (dhp->dh_flags & DEVMAP_ALLOW_REMAP) == 0)
                return (DDI_FAILURE);

        /* Only DEVMAP_MAPPING_INVALID flag supported for remap */
        if ((flags != 0) && (flags != DEVMAP_MAPPING_INVALID))
                return (DDI_FAILURE);

        if ((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) != dhp->dh_prot)
                return (DDI_FAILURE);

        if (!(flags & DEVMAP_MAPPING_INVALID)) {
                handle = impl_acc_hdl_alloc(KM_SLEEP, NULL);
                if (handle == NULL)
                        return (DDI_FAILURE);
        }

        HOLD_DHP_LOCK(dhp);

        /*
         * Unload the old mapping, so next fault will setup the new mappings
         * Do this while holding the dhp lock so other faults dont reestablish
         * the mappings
         */
        hat_unload(dhp->dh_seg->s_as->a_hat, dhp->dh_uvaddr,
            dhp->dh_len, HAT_UNLOAD|HAT_UNLOAD_OTHER);

        if (flags & DEVMAP_MAPPING_INVALID) {
                dhp->dh_flags |= DEVMAP_MAPPING_INVALID;
                dhp->dh_pfn = PFN_INVALID;
        } else {
                /* clear any prior DEVMAP_MAPPING_INVALID flag */
                dhp->dh_flags &= ~DEVMAP_MAPPING_INVALID;
                hp = impl_acc_hdl_get(handle);
                hp->ah_vers = VERS_ACCHDL;
                hp->ah_dip = dip;
                hp->ah_rnumber = rnumber;
                hp->ah_offset = roff;
                hp->ah_len = len;
                if (accattrp != NULL)
                        hp->ah_acc = *accattrp;

                mr.map_op = DDI_MO_MAP_LOCKED;
                mr.map_type = DDI_MT_RNUMBER;
                mr.map_obj.rnumber = rnumber;
                mr.map_prot = maxprot & dhp->dh_orig_maxprot;
                mr.map_flags = DDI_MF_DEVICE_MAPPING;
                mr.map_handlep = hp;
                mr.map_vers = DDI_MAP_VERSION;

                /*
                 * up the device tree to get pfn.
                 * The rootnex_map_regspec() routine in nexus drivers has been
                 * modified to return pfn if map_flags is DDI_MF_DEVICE_MAPPING.
                 */
                err = ddi_map(dip, &mr, roff, len, (caddr_t *)&pfn);
                hat_flags = hp->ah_hat_flags;
                impl_acc_hdl_free(handle);
                if (err) {
                        RELE_DHP_LOCK(dhp);
                        return (DDI_FAILURE);
                }
                /*
                 * Store result of ddi_map first in local variables, as we do
                 * not want to overwrite the existing dhp with wrong data.
                 */
                dhp->dh_pfn = pfn;
                dhp->dh_hat_attr = hat_flags;
        }

        /* clear the large page size flag */
        dhp->dh_flags &= ~DEVMAP_FLAG_LARGE;

        dhp->dh_cookie = DEVMAP_DEVMEM_COOKIE;
        dhp->dh_roff = ptob(btop(roff));

        /* setup the dh_mmulevel and DEVMAP_FLAG_LARGE */
        devmap_devmem_large_page_setup(dhp);
        dhp->dh_maxprot = maxprot & dhp->dh_orig_maxprot;
        ASSERT((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) == dhp->dh_prot);

        RELE_DHP_LOCK(dhp);
        return (DDI_SUCCESS);
}

/*
 * called by driver devmap routine to pass kernel virtual address  mapping
 * info to the framework.    used only for kernel memory
 * allocated from ddi_umem_alloc().
 */
int
devmap_umem_setup(devmap_cookie_t dhc, dev_info_t *dip,
    struct devmap_callback_ctl *callbackops, ddi_umem_cookie_t cookie,
    offset_t off, size_t len, uint_t maxprot, uint_t flags,
    ddi_device_acc_attr_t *accattrp)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        struct ddi_umem_cookie *cp = (struct ddi_umem_cookie *)cookie;


        DEBUGF(2, (CE_CONT, "devmap_umem_setup: dhp %p offset %llx "
            "cookie %p len %lx\n", (void *)dhp, off, (void *)cookie, len));

        if (cookie == NULL)
                return (DDI_FAILURE);

        /* For UMEM_TRASH, this restriction is not needed */
        if ((off + len) > cp->size)
                return (DDI_FAILURE);

        /* check if the cache attributes are supported */
        if (i_ddi_check_cache_attr(flags) == B_FALSE)
                return (DDI_FAILURE);

        /*
         * First to check if this function has been called for this dhp.
         */
        if (dhp->dh_flags & DEVMAP_SETUP_DONE)
                return (DDI_FAILURE);

        if ((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) != dhp->dh_prot)
                return (DDI_FAILURE);

        if (flags & DEVMAP_MAPPING_INVALID) {
                /*
                 * If DEVMAP_MAPPING_INVALID is specified, we have to grant
                 * remap permission.
                 */
                if (!(flags & DEVMAP_ALLOW_REMAP)) {
                        return (DDI_FAILURE);
                }
        } else {
                dhp->dh_cookie = cookie;
                dhp->dh_roff = ptob(btop(off));
                dhp->dh_cvaddr = cp->cvaddr + dhp->dh_roff;
                /* set HAT cache attributes */
                i_ddi_cacheattr_to_hatacc(flags, &dhp->dh_hat_attr);
                /* set HAT endianess attributes */
                i_ddi_devacc_to_hatacc(accattrp, &dhp->dh_hat_attr);
        }

        /*
         * The default is _not_ to pass HAT_LOAD_NOCONSIST to hat_devload();
         * we pass HAT_LOAD_NOCONSIST _only_ in cases where hat tries to
         * create consistent mappings but our intention was to create
         * non-consistent mappings.
         *
         * DEVMEM: hat figures it out it's DEVMEM and creates non-consistent
         * mappings.
         *
         * kernel exported memory: hat figures it out it's memory and always
         * creates consistent mappings.
         *
         * /dev/mem: non-consistent mappings. See comments in common/io/mem.c
         *
         * /dev/kmem: consistent mappings are created unless they are
         * MAP_FIXED. We _explicitly_ tell hat to create non-consistent
         * mappings by passing HAT_LOAD_NOCONSIST in case of MAP_FIXED
         * mappings of /dev/kmem. See common/io/mem.c
         */

        /* Only some of the flags bits are settable by the driver */
        dhp->dh_flags |= (flags & DEVMAP_SETUP_FLAGS);

        dhp->dh_len = ptob(btopr(len));
        dhp->dh_maxprot = maxprot & dhp->dh_orig_maxprot;
        ASSERT((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) == dhp->dh_prot);

        if (callbackops != NULL) {
                bcopy(callbackops, &dhp->dh_callbackops,
                    sizeof (struct devmap_callback_ctl));
        }
        /*
         * Initialize dh_lock if we want to do remap.
         */
        if (dhp->dh_flags & DEVMAP_ALLOW_REMAP) {
                mutex_init(&dhp->dh_lock, NULL, MUTEX_DEFAULT, NULL);
                dhp->dh_flags |= DEVMAP_LOCK_INITED;
        }

        dhp->dh_flags |= DEVMAP_SETUP_DONE;

        return (DDI_SUCCESS);
}

int
devmap_umem_remap(devmap_cookie_t dhc, dev_info_t *dip,
    ddi_umem_cookie_t cookie, offset_t off, size_t len, uint_t maxprot,
    uint_t flags, ddi_device_acc_attr_t *accattrp)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;
        struct ddi_umem_cookie *cp = (struct ddi_umem_cookie *)cookie;

        DEBUGF(2, (CE_CONT, "devmap_umem_remap: dhp %p offset %llx "
            "cookie %p len %lx\n", (void *)dhp, off, (void *)cookie, len));

        /*
         * Reture failure if setup has not been done or no remap permission
         * has been granted during the setup.
         */
        if ((dhp->dh_flags & DEVMAP_SETUP_DONE) == 0 ||
            (dhp->dh_flags & DEVMAP_ALLOW_REMAP) == 0)
                return (DDI_FAILURE);

        /* No flags supported for remap yet */
        if (flags != 0)
                return (DDI_FAILURE);

        /* check if the cache attributes are supported */
        if (i_ddi_check_cache_attr(flags) == B_FALSE)
                return (DDI_FAILURE);

        if ((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) != dhp->dh_prot)
                return (DDI_FAILURE);

        /* For UMEM_TRASH, this restriction is not needed */
        if ((off + len) > cp->size)
                return (DDI_FAILURE);

        HOLD_DHP_LOCK(dhp);
        /*
         * Unload the old mapping, so next fault will setup the new mappings
         * Do this while holding the dhp lock so other faults dont reestablish
         * the mappings
         */
        hat_unload(dhp->dh_seg->s_as->a_hat, dhp->dh_uvaddr,
            dhp->dh_len, HAT_UNLOAD|HAT_UNLOAD_OTHER);

        dhp->dh_cookie = cookie;
        dhp->dh_roff = ptob(btop(off));
        dhp->dh_cvaddr = cp->cvaddr + dhp->dh_roff;
        /* set HAT cache attributes */
        i_ddi_cacheattr_to_hatacc(flags, &dhp->dh_hat_attr);
        /* set HAT endianess attributes */
        i_ddi_devacc_to_hatacc(accattrp, &dhp->dh_hat_attr);

        /* clear the large page size flag */
        dhp->dh_flags &= ~DEVMAP_FLAG_LARGE;

        dhp->dh_maxprot = maxprot & dhp->dh_orig_maxprot;
        ASSERT((dhp->dh_prot & dhp->dh_orig_maxprot & maxprot) == dhp->dh_prot);
        RELE_DHP_LOCK(dhp);
        return (DDI_SUCCESS);
}

/*
 * to set timeout value for the driver's context management callback, e.g.
 * devmap_access().
 */
void
devmap_set_ctx_timeout(devmap_cookie_t dhc, clock_t ticks)
{
        devmap_handle_t *dhp = (devmap_handle_t *)dhc;

        dhp->dh_timeout_length = ticks;
}

int
devmap_default_access(devmap_cookie_t dhp, void *pvtp, offset_t off,
    size_t len, uint_t type, uint_t rw)
{

        return (devmap_load(dhp, off, len, type, rw));
}

/*
 * segkmem_alloc() wrapper to allocate memory which is both
 * non-relocatable (for DR) and sharelocked, since the rest
 * of this segment driver requires it.
 */
static void *
devmap_alloc_pages(vmem_t *vmp, size_t size, int vmflag)
{
        ASSERT(vmp != NULL);
        ASSERT(kvseg.s_base != NULL);
        vmflag |= (VM_NORELOC | SEGKMEM_SHARELOCKED);
        return (segkmem_alloc(vmp, size, vmflag));
}

/*
 * This is where things are a bit incestuous with seg_kmem: unlike
 * seg_kp, seg_kmem does not keep its pages long-term sharelocked, so
 * we need to do a bit of a dance around that to prevent duplication of
 * code until we decide to bite the bullet and implement a new kernel
 * segment for driver-allocated memory that is exported to user space.
 */
static void
devmap_free_pages(vmem_t *vmp, void *inaddr, size_t size)
{
        page_t *pp;
        caddr_t addr = inaddr;
        caddr_t eaddr;
        pgcnt_t npages = btopr(size);

        ASSERT(vmp != NULL);
        ASSERT(kvseg.s_base != NULL);
        ASSERT(((uintptr_t)addr & PAGEOFFSET) == 0);

        hat_unload(kas.a_hat, addr, size, HAT_UNLOAD_UNLOCK);

        for (eaddr = addr + size; addr < eaddr; addr += PAGESIZE) {
                /*
                 * Use page_find() instead of page_lookup() to find the page
                 * since we know that it is hashed and has a shared lock.
                 */
                pp = page_find(&kvp.v_object, (uoff_t)(uintptr_t)addr);

                if (pp == NULL)
                        panic("devmap_free_pages: page not found");
                if (!page_tryupgrade(pp)) {
                        page_unlock(pp);
                        pp = page_lookup(&kvp.v_object,
                                         (uoff_t)(uintptr_t)addr, SE_EXCL);
                        if (pp == NULL)
                                panic("devmap_free_pages: page already freed");
                }
                /* Clear p_lckcnt so page_destroy() doesn't update availrmem */
                pp->p_lckcnt = 0;
                page_destroy(pp, 0);
        }
        page_unresv(npages);

        if (vmp != NULL)
                vmem_free(vmp, inaddr, size);
}

/*
 * devmap_umem_alloc_np() replaces kmem_zalloc() as the method for
 * allocating non-pageable kmem in response to a ddi_umem_alloc()
 * default request. For now we allocate our own pages and we keep
 * them long-term sharelocked, since: A) the fault routines expect the
 * memory to already be locked; B) pageable umem is already long-term
 * locked; C) it's a lot of work to make it otherwise, particularly
 * since the nexus layer expects the pages to never fault. An RFE is to
 * not keep the pages long-term locked, but instead to be able to
 * take faults on them and simply look them up in kvp in case we
 * fault on them. Even then, we must take care not to let pageout
 * steal them from us since the data must remain resident; if we
 * do this we must come up with some way to pin the pages to prevent
 * faults while a driver is doing DMA to/from them.
 */
static void *
devmap_umem_alloc_np(size_t size, size_t flags)
{
        void *buf;
        int vmflags = (flags & DDI_UMEM_NOSLEEP)? VM_NOSLEEP : VM_SLEEP;

        buf = vmem_alloc(umem_np_arena, size, vmflags);
        if (buf != NULL)
                bzero(buf, size);
        return (buf);
}

static void
devmap_umem_free_np(void *addr, size_t size)
{
        vmem_free(umem_np_arena, addr, size);
}

/*
 * allocate page aligned kernel memory for exporting to user land.
 * The devmap framework will use the cookie allocated by ddi_umem_alloc()
 * to find a user virtual address that is in same color as the address
 * allocated here.
 */
void *
ddi_umem_alloc(size_t size, int flags, ddi_umem_cookie_t *cookie)
{
        register size_t len = ptob(btopr(size));
        void *buf = NULL;
        struct ddi_umem_cookie *cp;
        int iflags = 0;

        *cookie = NULL;

        if (len == 0)
                return (NULL);

        /*
         * allocate cookie
         */
        if ((cp = kmem_zalloc(sizeof (struct ddi_umem_cookie),
            flags & DDI_UMEM_NOSLEEP ? KM_NOSLEEP : KM_SLEEP)) == NULL) {
                ASSERT(flags & DDI_UMEM_NOSLEEP);
                return (NULL);
        }

        if (flags & DDI_UMEM_PAGEABLE) {
                /* Only one of the flags is allowed */
                ASSERT(!(flags & DDI_UMEM_TRASH));
                /* initialize resource with 0 */
                iflags = KPD_ZERO;

                /*
                 * to allocate unlocked pageable memory, use segkp_get() to
                 * create a segkp segment.  Since segkp can only service kas,
                 * other segment drivers such as segdev have to do
                 * as_fault(segkp, SOFTLOCK) in its fault routine,
                 */
                if (flags & DDI_UMEM_NOSLEEP)
                        iflags |= KPD_NOWAIT;

                if ((buf = segkp_get(segkp, len, iflags)) == NULL) {
                        kmem_free(cp, sizeof (struct ddi_umem_cookie));
                        return (NULL);
                }
                cp->type = KMEM_PAGEABLE;
                mutex_init(&cp->lock, NULL, MUTEX_DEFAULT, NULL);
                cp->locked = 0;
        } else if (flags & DDI_UMEM_TRASH) {
                /* Only one of the flags is allowed */
                ASSERT(!(flags & DDI_UMEM_PAGEABLE));
                cp->type = UMEM_TRASH;
                buf = NULL;
        } else {
                if ((buf = devmap_umem_alloc_np(len, flags)) == NULL) {
                        kmem_free(cp, sizeof (struct ddi_umem_cookie));
                        return (NULL);
                }

                cp->type = KMEM_NON_PAGEABLE;
        }

        /*
         * need to save size here.  size will be used when
         * we do kmem_free.
         */
        cp->size = len;
        cp->cvaddr = (caddr_t)buf;

        *cookie =  (void *)cp;
        return (buf);
}

void
ddi_umem_free(ddi_umem_cookie_t cookie)
{
        struct ddi_umem_cookie *cp;

        /*
         * if cookie is NULL, no effects on the system
         */
        if (cookie == NULL)
                return;

        cp = (struct ddi_umem_cookie *)cookie;

        switch (cp->type) {
        case KMEM_PAGEABLE :
                ASSERT(cp->cvaddr != NULL && cp->size != 0);
                /*
                 * Check if there are still any pending faults on the cookie
                 * while the driver is deleting it,
                 * XXX - could change to an ASSERT but wont catch errant drivers
                 */
                mutex_enter(&cp->lock);
                if (cp->locked) {
                        mutex_exit(&cp->lock);
                        panic("ddi_umem_free for cookie with pending faults %p",
                            (void *)cp);
                        return;
                }

                segkp_release(segkp, cp->cvaddr);

                /*
                 * release mutex associated with this cookie.
                 */
                mutex_destroy(&cp->lock);
                break;
        case KMEM_NON_PAGEABLE :
                ASSERT(cp->cvaddr != NULL && cp->size != 0);
                devmap_umem_free_np(cp->cvaddr, cp->size);
                break;
        case UMEM_TRASH :
                break;
        case UMEM_LOCKED :
                /* Callers should use ddi_umem_unlock for this type */
                ddi_umem_unlock(cookie);
                /* Frees the cookie too */
                return;
        default:
                /* panic so we can diagnose the underlying cause */
                panic("ddi_umem_free: illegal cookie type 0x%x\n",
                    cp->type);
        }

        kmem_free(cookie, sizeof (struct ddi_umem_cookie));
}


static int
segdev_getmemid(struct seg *seg, caddr_t addr, memid_t *memidp)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;

        /*
         * It looks as if it is always mapped shared
         */
        memidp->val[0] = (uintptr_t)VTOCVP(sdp->vp);
        memidp->val[1] = sdp->offset + (uintptr_t)(addr - seg->s_base);
        return (0);
}

/*
 * ddi_umem_alloc() non-pageable quantum cache max size.
 * This is just a SWAG.
 */
#define DEVMAP_UMEM_QUANTUM     (8*PAGESIZE)

/*
 * Initialize seg_dev from boot. This routine sets up the trash page
 * and creates the umem_np_arena used to back non-pageable memory
 * requests.
 */
void
segdev_init(void)
{
        struct seg kseg;

        vmobject_init(&trashvp.v_object, &trashvp);

        umem_np_arena = vmem_create("umem_np", NULL, 0, PAGESIZE,
            devmap_alloc_pages, devmap_free_pages, heap_arena,
            DEVMAP_UMEM_QUANTUM, VM_SLEEP);

        kseg.s_as = &kas;
        trashpp = page_create_va(&trashvp.v_object, 0, PAGESIZE,
            PG_NORELOC | PG_EXCL | PG_WAIT, &kseg, NULL);
        if (trashpp == NULL)
                panic("segdev_init: failed to create trash page");
        pagezero(trashpp, 0, PAGESIZE);
        page_downgrade(trashpp);
}

/*
 * Invoke platform-dependent support routines so that /proc can have
 * the platform code deal with curious hardware.
 */
int
segdev_copyfrom(struct seg *seg,
    caddr_t uaddr, const void *devaddr, void *kaddr, size_t len)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        struct snode *sp = VTOS(VTOCVP(sdp->vp));

        return (e_ddi_copyfromdev(sp->s_dip,
            (off_t)(uaddr - seg->s_base), devaddr, kaddr, len));
}

int
segdev_copyto(struct seg *seg,
    caddr_t uaddr, const void *kaddr, void *devaddr, size_t len)
{
        struct segdev_data *sdp = (struct segdev_data *)seg->s_data;
        struct snode *sp = VTOS(VTOCVP(sdp->vp));

        return (e_ddi_copytodev(sp->s_dip,
            (off_t)(uaddr - seg->s_base), kaddr, devaddr, len));
}