kernel - Many fixes for vkernel support, plus a few main kernel fixes

[dragonfly.git] / sys / platform / pc64 / x86_64 / pmap_inval.c

/*
 * Copyright (c) 2003-2011 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * pmap invalidation support code.  Certain hardware requirements must
 * be dealt with when manipulating page table entries and page directory
 * entries within a pmap.  In particular, we cannot safely manipulate
 * page tables which are in active use by another cpu (even if it is
 * running in userland) for two reasons: First, TLB writebacks will
 * race against our own modifications and tests.  Second, even if we
 * were to use bus-locked instruction we can still screw up the 
 * target cpu's instruction pipeline due to Intel cpu errata.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/vmmeter.h>
#include <sys/thread2.h>
#include <sys/sysctl.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_object.h>

#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <machine/smp.h>
#include <machine/globaldata.h>
#include <machine/pmap.h>
#include <machine/pmap_inval.h>
#include <machine/clock.h>

#if 1   /* DEBUGGING */
#define LOOPRECOVER                     /* enable watchdog */
#endif

/*
 * Watchdog recovery interval, in seconds.
 *
 * The watchdog value is generous for two reasons.  First, because the
 * situation is not supposed to happen at all (but does), and second,
 * because VMs could be very slow at handling IPIs.
 */
#define LOOPRECOVER_TIMEOUT1    2       /* initial recovery */
#define LOOPRECOVER_TIMEOUT2    1       /* repeated recoveries */

#define MAX_INVAL_PAGES         128

struct pmap_inval_info {
        vm_offset_t     va;
        pt_entry_t      *ptep;
        pt_entry_t      opte;
        pt_entry_t      npte;
        enum { INVDONE, INVSTORE, INVCMPSET } mode;
        int             success;
        vm_pindex_t     npgs;
        cpumask_t       done;
        cpumask_t       mask;
#ifdef LOOPRECOVER
        cpumask_t       sigmask;
        int             failed;
        int64_t         tsc_target;
#endif
} __cachealign;

typedef struct pmap_inval_info pmap_inval_info_t;

static pmap_inval_info_t        invinfo[MAXCPU];
extern cpumask_t                smp_invmask;
#ifdef LOOPRECOVER
#ifdef LOOPMASK_IN
extern cpumask_t                smp_in_mask;
#endif
extern cpumask_t                smp_smurf_mask;
#endif
static int pmap_inval_watchdog_print;   /* must always default off */
static int pmap_inval_force_allcpus;
static int pmap_inval_force_nonopt;

SYSCTL_INT(_machdep, OID_AUTO, pmap_inval_watchdog_print, CTLFLAG_RW,
            &pmap_inval_watchdog_print, 0, "");
SYSCTL_INT(_machdep, OID_AUTO, pmap_inval_force_allcpus, CTLFLAG_RW,
            &pmap_inval_force_allcpus, 0, "");
SYSCTL_INT(_machdep, OID_AUTO, pmap_inval_force_nonopt, CTLFLAG_RW,
            &pmap_inval_force_nonopt, 0, "");

static void
pmap_inval_init(pmap_t pmap)
{
        cpulock_t olock;
        cpulock_t nlock;

        crit_enter_id("inval");

        if (pmap != &kernel_pmap) {
                for (;;) {
                        olock = pmap->pm_active_lock;
                        cpu_ccfence();
                        nlock = olock | CPULOCK_EXCL;
                        if (olock != nlock &&
                            atomic_cmpset_int(&pmap->pm_active_lock,
                                              olock, nlock)) {
                                break;
                        }
                        lwkt_process_ipiq();
                        cpu_pause();
                }
                atomic_add_acq_long(&pmap->pm_invgen, 1);
        }
}

static void
pmap_inval_done(pmap_t pmap)
{
        if (pmap != &kernel_pmap) {
                atomic_add_acq_long(&pmap->pm_invgen, 1);
                atomic_clear_int(&pmap->pm_active_lock, CPULOCK_EXCL);
        }
        crit_exit_id("inval");
}

#ifdef LOOPRECOVER

/*
 * Debugging and lost IPI recovery code.
 */
static
__inline
int
loopwdog(struct pmap_inval_info *info)
{
        int64_t tsc;

        tsc = rdtsc();
        if (info->tsc_target - tsc < 0 && tsc_frequency) {
                info->tsc_target = tsc + (tsc_frequency * LOOPRECOVER_TIMEOUT2);
                return 1;
        }
        return 0;
}

static
void
loopdebug(const char *msg, pmap_inval_info_t *info)
{
        int p;
        int cpu = mycpu->gd_cpuid;

        /*
         * Don't kprintf() anything if the pmap inval watchdog gets hit.
         * DRM can cause an occassional watchdog hit (at least with a 1/16
         * second watchdog), and attempting to kprintf to the KVM frame buffer
         * from Xinvltlb, which ignores critical sections, can implode the
         * system.
         */
        if (pmap_inval_watchdog_print == 0)
                return;

        cpu_lfence();
#ifdef LOOPRECOVER
        atomic_add_long(&smp_smurf_mask.ary[0], 0);
#endif
        kprintf("ipilost-%s! %d mode=%d m=%08jx d=%08jx "
#ifdef LOOPRECOVER
                "s=%08jx "
#endif
#ifdef LOOPMASK_IN
                "in=%08jx "
#endif
#ifdef LOOPRECOVER
                "smurf=%08jx\n"
#endif
                , msg, cpu, info->mode,
                info->mask.ary[0],
                info->done.ary[0]
#ifdef LOOPRECOVER
                , info->sigmask.ary[0]
#endif
#ifdef LOOPMASK_IN
                , smp_in_mask.ary[0]
#endif
#ifdef LOOPRECOVER
                , smp_smurf_mask.ary[0]
#endif
                );
        kprintf("mdglob ");
        for (p = 0; p < ncpus; ++p)
                kprintf(" %d", CPU_prvspace[p]->mdglobaldata.gd_xinvaltlb);
        kprintf("\n");
}

#endif

#ifdef CHECKSIG

#define CHECKSIGMASK(info)      _checksigmask(info, __FILE__, __LINE__)

static
void
_checksigmask(pmap_inval_info_t *info, const char *file, int line)
{
        cpumask_t tmp;

        tmp = info->mask;
        CPUMASK_ANDMASK(tmp, info->sigmask);
        if (CPUMASK_CMPMASKNEQ(tmp, info->mask)) {
                kprintf("\"%s\" line %d: bad sig/mask %08jx %08jx\n",
                        file, line, info->sigmask.ary[0], info->mask.ary[0]);
        }
}

#else

#define CHECKSIGMASK(info)

#endif

/*
 * Invalidate the specified va across all cpus associated with the pmap.
 * If va == (vm_offset_t)-1, we invltlb() instead of invlpg().  The operation
 * will be done fully synchronously with storing npte into *ptep and returning
 * opte.
 *
 * If ptep is NULL the operation will execute semi-synchronously.
 * ptep must be NULL if npgs > 1
 */
pt_entry_t
pmap_inval_smp(pmap_t pmap, vm_offset_t va, vm_pindex_t npgs,
               pt_entry_t *ptep, pt_entry_t npte)
{
        globaldata_t gd = mycpu;
        pmap_inval_info_t *info;
        pt_entry_t opte = 0;
        int cpu = gd->gd_cpuid;
        cpumask_t tmpmask;
        unsigned long rflags;

        /*
         * Initialize invalidation for pmap and enter critical section.
         * This will enter a critical section for us.
         */
        if (pmap == NULL)
                pmap = &kernel_pmap;
        pmap_inval_init(pmap);

        /*
         * Shortcut single-cpu case if possible.
         */
        if (CPUMASK_CMPMASKEQ(pmap->pm_active, gd->gd_cpumask) &&
            pmap_inval_force_nonopt == 0) {
                /*
                 * Convert to invltlb if there are too many pages to
                 * invlpg on.
                 */
                if (npgs == 1) {
                        if (ptep)
                                opte = atomic_swap_long(ptep, npte);
                        if (va == (vm_offset_t)-1)
                                cpu_invltlb();
                        else
                                cpu_invlpg((void *)va);
                } else if (va == (vm_offset_t)-1 || npgs > MAX_INVAL_PAGES) {
                        if (ptep) {
                                while (npgs) {
                                        opte = atomic_swap_long(ptep, npte);
                                        ++ptep;
                                        --npgs;
                                }
                        }
                        cpu_invltlb();
                } else {
                        while (npgs) {
                                if (ptep) {
                                        opte = atomic_swap_long(ptep, npte);
                                        ++ptep;
                                }
                                cpu_invlpg((void *)va);
                                va += PAGE_SIZE;
                                --npgs;
                        }
                }
                pmap_inval_done(pmap);

                return opte;
        }

        /*
         * We need a critical section to prevent getting preempted while
         * we setup our command.  A preemption might execute its own
         * pmap_inval*() command and create confusion below.
         *
         * tsc_target is our watchdog timeout that will attempt to recover
         * from a lost IPI.  Set to 1/16 second for now.
         */
        info = &invinfo[cpu];

        /*
         * We must wait for other cpus which may still be finishing up a
         * prior operation that we requested.
         *
         * We do not have to disable interrupts here.  An Xinvltlb can occur
         * at any time (even within a critical section), but it will not
         * act on our command until we set our done bits.
         */
        while (CPUMASK_TESTNZERO(info->done)) {
#ifdef LOOPRECOVER
                if (loopwdog(info)) {
                        info->failed = 1;
                        loopdebug("A", info);
                        /* XXX recover from possible bug */
                        CPUMASK_ASSZERO(info->done);
                }
#endif
                cpu_pause();
        }
        KKASSERT(info->mode == INVDONE);
        cpu_mfence();

        /*
         * Must set our cpu in the invalidation scan mask before
         * any possibility of [partial] execution (remember, XINVLTLB
         * can interrupt a critical section).
         */
        ATOMIC_CPUMASK_ORBIT(smp_invmask, cpu);

        info->tsc_target = rdtsc() + (tsc_frequency * LOOPRECOVER_TIMEOUT1);
        info->va = va;
        info->npgs = npgs;
        info->ptep = ptep;
        info->npte = npte;
        info->opte = 0;
#ifdef LOOPRECOVER
        info->failed = 0;
#endif
        info->mode = INVSTORE;

        tmpmask = pmap->pm_active;      /* volatile (bits may be cleared) */
        if (pmap_inval_force_allcpus)
                tmpmask = smp_active_mask;
        cpu_ccfence();
        CPUMASK_ANDMASK(tmpmask, smp_active_mask);

        /*
         * If ptep is NULL the operation can be semi-synchronous, which means
         * we can improve performance by flagging and removing idle cpus
         * (see the idleinvlclr function in mp_machdep.c).
         *
         * Typically kernel page table operation is semi-synchronous.
         */
        if (ptep == NULL)
                smp_smurf_idleinvlclr(&tmpmask);
        CPUMASK_ORBIT(tmpmask, cpu);
        info->mask = tmpmask;

        /*
         * Command may start executing the moment 'done' is initialized,
         * disable current cpu interrupt to prevent 'done' field from
         * changing (other cpus can't clear done bits until the originating
         * cpu clears its mask bit, but other cpus CAN start clearing their
         * mask bits).
         */
#ifdef LOOPRECOVER
        info->sigmask = tmpmask;
        CHECKSIGMASK(info);
#endif
        cpu_sfence();
        rflags = read_rflags();
        cpu_disable_intr();

        ATOMIC_CPUMASK_COPY(info->done, tmpmask);
        /* execution can begin here on other cpus due to races */

        /*
         * Pass our copy of the done bits (so they don't change out from
         * under us) to generate the Xinvltlb interrupt on the targets.
         */
        smp_invlpg(&tmpmask);
        opte = info->opte;
        KKASSERT(info->mode == INVDONE);

        /*
         * Target cpus will be in their loop exiting concurrently with our
         * cleanup.  They will not lose the bitmask they obtained before so
         * we can safely clear this bit.
         */
        ATOMIC_CPUMASK_NANDBIT(smp_invmask, cpu);
        write_rflags(rflags);
        pmap_inval_done(pmap);

        return opte;
}

/*
 * API function - invalidate the pte at (va) and replace *ptep with npte
 * atomically only if *ptep equals opte, across the pmap's active cpus.
 *
 * Returns 1 on success, 0 on failure (caller typically retries).
 */
int
pmap_inval_smp_cmpset(pmap_t pmap, vm_offset_t va, pt_entry_t *ptep,
                      pt_entry_t opte, pt_entry_t npte)
{
        globaldata_t gd = mycpu;
        pmap_inval_info_t *info;
        int success;
        int cpu = gd->gd_cpuid;
        cpumask_t tmpmask;
        unsigned long rflags;

        /*
         * Initialize invalidation for pmap and enter critical section.
         */
        if (pmap == NULL)
                pmap = &kernel_pmap;
        pmap_inval_init(pmap);

        /*
         * Shortcut single-cpu case if possible.
         */
        if (CPUMASK_CMPMASKEQ(pmap->pm_active, gd->gd_cpumask) &&
            pmap_inval_force_nonopt == 0) {
                if (atomic_cmpset_long(ptep, opte, npte)) {
                        if (va == (vm_offset_t)-1)
                                cpu_invltlb();
                        else
                                cpu_invlpg((void *)va);
                        pmap_inval_done(pmap);
                        return 1;
                } else {
                        pmap_inval_done(pmap);
                        return 0;
                }
        }

        /*
         * We need a critical section to prevent getting preempted while
         * we setup our command.  A preemption might execute its own
         * pmap_inval*() command and create confusion below.
         */
        info = &invinfo[cpu];

        /*
         * We must wait for other cpus which may still be finishing
         * up a prior operation.
         */
        while (CPUMASK_TESTNZERO(info->done)) {
#ifdef LOOPRECOVER
                if (loopwdog(info)) {
                        info->failed = 1;
                        loopdebug("B", info);
                        /* XXX recover from possible bug */
                        CPUMASK_ASSZERO(info->done);
                }
#endif
                cpu_pause();
        }
        KKASSERT(info->mode == INVDONE);
        cpu_mfence();

        /*
         * Must set our cpu in the invalidation scan mask before
         * any possibility of [partial] execution (remember, XINVLTLB
         * can interrupt a critical section).
         */
        ATOMIC_CPUMASK_ORBIT(smp_invmask, cpu);

        info->tsc_target = rdtsc() + (tsc_frequency * LOOPRECOVER_TIMEOUT1);
        info->va = va;
        info->npgs = 1;                 /* unused */
        info->ptep = ptep;
        info->npte = npte;
        info->opte = opte;
#ifdef LOOPRECOVER
        info->failed = 0;
#endif
        info->mode = INVCMPSET;
        info->success = 0;

        tmpmask = pmap->pm_active;      /* volatile */
        if (pmap_inval_force_allcpus)
                tmpmask = smp_active_mask;
        cpu_ccfence();
        CPUMASK_ANDMASK(tmpmask, smp_active_mask);
        CPUMASK_ORBIT(tmpmask, cpu);
        info->mask = tmpmask;

        /*
         * Command may start executing the moment 'done' is initialized,
         * disable current cpu interrupt to prevent 'done' field from
         * changing (other cpus can't clear done bits until the originating
         * cpu clears its mask bit).
         */
#ifdef LOOPRECOVER
        info->sigmask = tmpmask;
        CHECKSIGMASK(info);
#endif
        cpu_sfence();
        rflags = read_rflags();
        cpu_disable_intr();

        ATOMIC_CPUMASK_COPY(info->done, tmpmask);

        /*
         * Pass our copy of the done bits (so they don't change out from
         * under us) to generate the Xinvltlb interrupt on the targets.
         */
        smp_invlpg(&tmpmask);
        success = info->success;
        KKASSERT(info->mode == INVDONE);

        ATOMIC_CPUMASK_NANDBIT(smp_invmask, cpu);
        write_rflags(rflags);
        pmap_inval_done(pmap);

        return success;
}

void
pmap_inval_bulk_init(pmap_inval_bulk_t *bulk, struct pmap *pmap)
{
        bulk->pmap = pmap;
        bulk->va_beg = 0;
        bulk->va_end = 0;
        bulk->count = 0;
}

pt_entry_t
pmap_inval_bulk(pmap_inval_bulk_t *bulk, vm_offset_t va,
                pt_entry_t *ptep, pt_entry_t npte)
{
        pt_entry_t pte;

        /*
         * Degenerate case, localized or we don't care (e.g. because we
         * are jacking the entire page table) or the pmap is not in-use
         * by anyone.  No invalidations are done on any cpu.
         */
        if (bulk == NULL) {
                pte = atomic_swap_long(ptep, npte);
                return pte;
        }

        /*
         * If it isn't the kernel pmap we execute the operation synchronously
         * on all cpus belonging to the pmap, which avoids concurrency bugs in
         * the hw related to changing pte's out from under threads.
         *
         * Eventually I would like to implement streaming pmap invalidation
         * for user pmaps to reduce mmap/munmap overheads for heavily-loaded
         * threaded programs.
         */
        if (bulk->pmap != &kernel_pmap) {
                pte = pmap_inval_smp(bulk->pmap, va, 1, ptep, npte);
                return pte;
        }

        /*
         * This is the kernel_pmap.  All unmap operations presume that there
         * are no other cpus accessing the addresses in question.  Implement
         * the bulking algorithm.  collect the required information and
         * synchronize once at the end.
         */
        pte = atomic_swap_long(ptep, npte);
        if (va == (vm_offset_t)-1) {
                bulk->va_beg = va;
        } else if (bulk->va_beg == bulk->va_end) {
                bulk->va_beg = va;
                bulk->va_end = va + PAGE_SIZE;
        } else if (va == bulk->va_end) {
                bulk->va_end = va + PAGE_SIZE;
        } else {
                bulk->va_beg = (vm_offset_t)-1;
                bulk->va_end = 0;
#if 0
                pmap_inval_bulk_flush(bulk);
                bulk->count = 1;
                if (va == (vm_offset_t)-1) {
                        bulk->va_beg = va;
                        bulk->va_end = 0;
                } else {
                        bulk->va_beg = va;
                        bulk->va_end = va + PAGE_SIZE;
                }
#endif
        }
        ++bulk->count;

        return pte;
}

void
pmap_inval_bulk_flush(pmap_inval_bulk_t *bulk)
{
        if (bulk == NULL)
                return;
        if (bulk->va_beg != bulk->va_end) {
                if (bulk->va_beg == (vm_offset_t)-1) {
                        pmap_inval_smp(bulk->pmap, bulk->va_beg, 1, NULL, 0);
                } else {
                        vm_pindex_t n;

                        n = (bulk->va_end - bulk->va_beg) >> PAGE_SHIFT;
                        pmap_inval_smp(bulk->pmap, bulk->va_beg, n, NULL, 0);
                }
        }
        bulk->va_beg = 0;
        bulk->va_end = 0;
        bulk->count = 0;
}

/*
 * Called from Xinvl with a critical section held and interrupts enabled.
 */
int
pmap_inval_intr(cpumask_t *cpumaskp, int toolong)
{
        globaldata_t gd = mycpu;
        pmap_inval_info_t *info;
        int loopme = 0;
        int cpu;
        cpumask_t cpumask;

        /*
         * Check all cpus for invalidations we may need to service.
         */
        cpu_ccfence();
        cpu = gd->gd_cpuid;
        cpumask = *cpumaskp;

        while (CPUMASK_TESTNZERO(cpumask)) {
                int n = BSFCPUMASK(cpumask);

#ifdef LOOPRECOVER
                KKASSERT(n >= 0 && n < MAXCPU);
#endif

                CPUMASK_NANDBIT(cpumask, n);
                info = &invinfo[n];

                /*
                 * Checkout cpu (cpu) for work in the target cpu info (n)
                 *
                 * if (n == cpu) - check our cpu for a master operation
                 * if (n != cpu) - check other cpus for a slave operation
                 *
                 * Due to interrupts/races we can catch a new operation
                 * in an older interrupt in other cpus.
                 *
                 * A fence is needed once we detect the (not) done bit.
                 */
                if (!CPUMASK_TESTBIT(info->done, cpu))
                        continue;
                cpu_lfence();
#ifdef LOOPRECOVER
                if (toolong) {
                        kprintf("pminvl %d->%d %08jx %08jx mode=%d\n",
                                cpu, n, info->done.ary[0], info->mask.ary[0],
                                info->mode);
                }
#endif

                /*
                 * info->mask and info->done always contain the originating
                 * cpu until the originator is done.  Targets may still be
                 * present in info->done after the originator is done (they
                 * will be finishing up their loops).
                 *
                 * Clear info->mask bits on other cpus to indicate that they
                 * have quiesced (entered the loop).  Once the other mask bits
                 * are clear we can execute the operation on the original,
                 * then clear the mask and done bits on the originator.  The
                 * targets will then finish up their side and clear their
                 * done bits.
                 *
                 * The command is considered 100% done when all done bits have
                 * been cleared.
                 */
                if (n != cpu) {
                        /*
                         * Command state machine for 'other' cpus.
                         */
                        if (CPUMASK_TESTBIT(info->mask, cpu)) {
                                /*
                                 * Other cpus indicate to originator that they
                                 * are quiesced.
                                 */
                                ATOMIC_CPUMASK_NANDBIT(info->mask, cpu);
                                loopme = 1;
                        } else if (info->ptep &&
                                   CPUMASK_TESTBIT(info->mask, n)) {
                                /*
                                 * Other cpu must wait for the originator (n)
                                 * to complete its command if ptep is not NULL.
                                 */
                                loopme = 1;
                        } else {
                                /*
                                 * Other cpu detects that the originator has
                                 * completed its command, or there was no
                                 * command.
                                 *
                                 * Now that the page table entry has changed,
                                 * we can follow up with our own invalidation.
                                 */
                                vm_offset_t va = info->va;
                                vm_pindex_t npgs;

                                if (va == (vm_offset_t)-1 ||
                                    info->npgs > MAX_INVAL_PAGES) {
                                        cpu_invltlb();
                                } else {
                                        for (npgs = info->npgs; npgs; --npgs) {
                                                cpu_invlpg((void *)va);
                                                va += PAGE_SIZE;
                                        }
                                }
                                ATOMIC_CPUMASK_NANDBIT(info->done, cpu);
                                /* info invalid now */
                                /* loopme left alone */
                        }
                } else if (CPUMASK_TESTBIT(info->mask, cpu)) {
                        /*
                         * Originator is waiting for other cpus
                         */
                        if (CPUMASK_CMPMASKNEQ(info->mask, gd->gd_cpumask)) {
                                /*
                                 * Originator waits for other cpus to enter
                                 * their loop (aka quiesce).
                                 *
                                 * If this bugs out the IPI may have been lost,
                                 * try to reissue by resetting our own
                                 * reentrancy bit and clearing the smurf mask
                                 * for the cpus that did not respond, then
                                 * reissuing the IPI.
                                 */
                                loopme = 1;
#ifdef LOOPRECOVER
                                if (loopwdog(info)) {
                                        info->failed = 1;
                                        loopdebug("C", info);
                                        /* XXX recover from possible bug */
                                        mdcpu->gd_xinvaltlb = 0;
                                        ATOMIC_CPUMASK_NANDMASK(smp_smurf_mask,
                                                                info->mask);
                                        cpu_disable_intr();
                                        smp_invlpg(&smp_active_mask);

                                        /*
                                         * Force outer-loop retest of Xinvltlb
                                         * requests (see mp_machdep.c).
                                         */
                                        mdcpu->gd_xinvaltlb = 2;
                                        cpu_enable_intr();
                                }
#endif
                        } else {
                                /*
                                 * Originator executes operation and clears
                                 * mask to allow other cpus to finish.
                                 */
                                KKASSERT(info->mode != INVDONE);
                                if (info->mode == INVSTORE) {
                                        if (info->ptep)
                                                info->opte = atomic_swap_long(info->ptep, info->npte);
                                        CHECKSIGMASK(info);
                                        ATOMIC_CPUMASK_NANDBIT(info->mask, cpu);
                                        CHECKSIGMASK(info);
                                } else {
                                        if (atomic_cmpset_long(info->ptep,
                                                              info->opte, info->npte)) {
                                                info->success = 1;
                                        } else {
                                                info->success = 0;
                                        }
                                        CHECKSIGMASK(info);
                                        ATOMIC_CPUMASK_NANDBIT(info->mask, cpu);
                                        CHECKSIGMASK(info);
                                }
                                loopme = 1;
                        }
                } else {
                        /*
                         * Originator does not have to wait for the other
                         * cpus to finish.  It clears its done bit.  A new
                         * command will not be initiated by the originator
                         * until the other cpus have cleared their done bits
                         * (asynchronously).
                         */
                        vm_offset_t va = info->va;
                        vm_pindex_t npgs;

                        if (va == (vm_offset_t)-1 ||
                            info->npgs > MAX_INVAL_PAGES) {
                                cpu_invltlb();
                        } else {
                                for (npgs = info->npgs; npgs; --npgs) {
                                        cpu_invlpg((void *)va);
                                        va += PAGE_SIZE;
                                }
                        }

                        /* leave loopme alone */
                        /* other cpus may still be finishing up */
                        /* can't race originator since that's us */
                        info->mode = INVDONE;
                        ATOMIC_CPUMASK_NANDBIT(info->done, cpu);
                }
        }
        return loopme;
}