powerpc: Add PPC_EMULATED_STATS to powernv_defconfig

[linux-2.6/btrfs-unstable.git] / drivers / iommu / iova.c

/*
 * Copyright © 2006-2009, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Author: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
 */

#include <linux/iova.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/bitops.h>
#include <linux/cpu.h>

static bool iova_rcache_insert(struct iova_domain *iovad,
                               unsigned long pfn,
                               unsigned long size);
static unsigned long iova_rcache_get(struct iova_domain *iovad,
                                     unsigned long size,
                                     unsigned long limit_pfn);
static void init_iova_rcaches(struct iova_domain *iovad);
static void free_iova_rcaches(struct iova_domain *iovad);
static void fq_destroy_all_entries(struct iova_domain *iovad);
static void fq_flush_timeout(unsigned long data);

void
init_iova_domain(struct iova_domain *iovad, unsigned long granule,
        unsigned long start_pfn, unsigned long pfn_32bit)
{
        /*
         * IOVA granularity will normally be equal to the smallest
         * supported IOMMU page size; both *must* be capable of
         * representing individual CPU pages exactly.
         */
        BUG_ON((granule > PAGE_SIZE) || !is_power_of_2(granule));

        spin_lock_init(&iovad->iova_rbtree_lock);
        iovad->rbroot = RB_ROOT;
        iovad->cached32_node = NULL;
        iovad->granule = granule;
        iovad->start_pfn = start_pfn;
        iovad->dma_32bit_pfn = pfn_32bit + 1;
        iovad->flush_cb = NULL;
        iovad->fq = NULL;
        init_iova_rcaches(iovad);
}
EXPORT_SYMBOL_GPL(init_iova_domain);

static void free_iova_flush_queue(struct iova_domain *iovad)
{
        if (!iovad->fq)
                return;

        if (timer_pending(&iovad->fq_timer))
                del_timer(&iovad->fq_timer);

        fq_destroy_all_entries(iovad);

        free_percpu(iovad->fq);

        iovad->fq         = NULL;
        iovad->flush_cb   = NULL;
        iovad->entry_dtor = NULL;
}

int init_iova_flush_queue(struct iova_domain *iovad,
                          iova_flush_cb flush_cb, iova_entry_dtor entry_dtor)
{
        int cpu;

        atomic64_set(&iovad->fq_flush_start_cnt,  0);
        atomic64_set(&iovad->fq_flush_finish_cnt, 0);

        iovad->fq = alloc_percpu(struct iova_fq);
        if (!iovad->fq)
                return -ENOMEM;

        iovad->flush_cb   = flush_cb;
        iovad->entry_dtor = entry_dtor;

        for_each_possible_cpu(cpu) {
                struct iova_fq *fq;

                fq = per_cpu_ptr(iovad->fq, cpu);
                fq->head = 0;
                fq->tail = 0;

                spin_lock_init(&fq->lock);
        }

        setup_timer(&iovad->fq_timer, fq_flush_timeout, (unsigned long)iovad);
        atomic_set(&iovad->fq_timer_on, 0);

        return 0;
}
EXPORT_SYMBOL_GPL(init_iova_flush_queue);

static struct rb_node *
__get_cached_rbnode(struct iova_domain *iovad, unsigned long *limit_pfn)
{
        if ((*limit_pfn > iovad->dma_32bit_pfn) ||
                (iovad->cached32_node == NULL))
                return rb_last(&iovad->rbroot);
        else {
                struct rb_node *prev_node = rb_prev(iovad->cached32_node);
                struct iova *curr_iova =
                        rb_entry(iovad->cached32_node, struct iova, node);
                *limit_pfn = curr_iova->pfn_lo;
                return prev_node;
        }
}

static void
__cached_rbnode_insert_update(struct iova_domain *iovad,
        unsigned long limit_pfn, struct iova *new)
{
        if (limit_pfn != iovad->dma_32bit_pfn)
                return;
        iovad->cached32_node = &new->node;
}

static void
__cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
{
        struct iova *cached_iova;
        struct rb_node *curr;

        if (!iovad->cached32_node)
                return;
        curr = iovad->cached32_node;
        cached_iova = rb_entry(curr, struct iova, node);

        if (free->pfn_lo >= cached_iova->pfn_lo) {
                struct rb_node *node = rb_next(&free->node);
                struct iova *iova = rb_entry(node, struct iova, node);

                /* only cache if it's below 32bit pfn */
                if (node && iova->pfn_lo < iovad->dma_32bit_pfn)
                        iovad->cached32_node = node;
                else
                        iovad->cached32_node = NULL;
        }
}

/* Insert the iova into domain rbtree by holding writer lock */
static void
iova_insert_rbtree(struct rb_root *root, struct iova *iova,
                   struct rb_node *start)
{
        struct rb_node **new, *parent = NULL;

        new = (start) ? &start : &(root->rb_node);
        /* Figure out where to put new node */
        while (*new) {
                struct iova *this = rb_entry(*new, struct iova, node);

                parent = *new;

                if (iova->pfn_lo < this->pfn_lo)
                        new = &((*new)->rb_left);
                else if (iova->pfn_lo > this->pfn_lo)
                        new = &((*new)->rb_right);
                else {
                        WARN_ON(1); /* this should not happen */
                        return;
                }
        }
        /* Add new node and rebalance tree. */
        rb_link_node(&iova->node, parent, new);
        rb_insert_color(&iova->node, root);
}

/*
 * Computes the padding size required, to make the start address
 * naturally aligned on the power-of-two order of its size
 */
static unsigned int
iova_get_pad_size(unsigned int size, unsigned int limit_pfn)
{
        return (limit_pfn - size) & (__roundup_pow_of_two(size) - 1);
}

static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
                unsigned long size, unsigned long limit_pfn,
                        struct iova *new, bool size_aligned)
{
        struct rb_node *prev, *curr = NULL;
        unsigned long flags;
        unsigned long saved_pfn;
        unsigned int pad_size = 0;

        /* Walk the tree backwards */
        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        saved_pfn = limit_pfn;
        curr = __get_cached_rbnode(iovad, &limit_pfn);
        prev = curr;
        while (curr) {
                struct iova *curr_iova = rb_entry(curr, struct iova, node);

                if (limit_pfn <= curr_iova->pfn_lo) {
                        goto move_left;
                } else if (limit_pfn > curr_iova->pfn_hi) {
                        if (size_aligned)
                                pad_size = iova_get_pad_size(size, limit_pfn);
                        if ((curr_iova->pfn_hi + size + pad_size) < limit_pfn)
                                break;  /* found a free slot */
                }
                limit_pfn = curr_iova->pfn_lo;
move_left:
                prev = curr;
                curr = rb_prev(curr);
        }

        if (!curr) {
                if (size_aligned)
                        pad_size = iova_get_pad_size(size, limit_pfn);
                if ((iovad->start_pfn + size + pad_size) > limit_pfn) {
                        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
                        return -ENOMEM;
                }
        }

        /* pfn_lo will point to size aligned address if size_aligned is set */
        new->pfn_lo = limit_pfn - (size + pad_size);
        new->pfn_hi = new->pfn_lo + size - 1;

        /* If we have 'prev', it's a valid place to start the insertion. */
        iova_insert_rbtree(&iovad->rbroot, new, prev);
        __cached_rbnode_insert_update(iovad, saved_pfn, new);

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);


        return 0;
}

static struct kmem_cache *iova_cache;
static unsigned int iova_cache_users;
static DEFINE_MUTEX(iova_cache_mutex);

struct iova *alloc_iova_mem(void)
{
        return kmem_cache_alloc(iova_cache, GFP_ATOMIC);
}
EXPORT_SYMBOL(alloc_iova_mem);

void free_iova_mem(struct iova *iova)
{
        kmem_cache_free(iova_cache, iova);
}
EXPORT_SYMBOL(free_iova_mem);

int iova_cache_get(void)
{
        mutex_lock(&iova_cache_mutex);
        if (!iova_cache_users) {
                iova_cache = kmem_cache_create(
                        "iommu_iova", sizeof(struct iova), 0,
                        SLAB_HWCACHE_ALIGN, NULL);
                if (!iova_cache) {
                        mutex_unlock(&iova_cache_mutex);
                        printk(KERN_ERR "Couldn't create iova cache\n");
                        return -ENOMEM;
                }
        }

        iova_cache_users++;
        mutex_unlock(&iova_cache_mutex);

        return 0;
}
EXPORT_SYMBOL_GPL(iova_cache_get);

void iova_cache_put(void)
{
        mutex_lock(&iova_cache_mutex);
        if (WARN_ON(!iova_cache_users)) {
                mutex_unlock(&iova_cache_mutex);
                return;
        }
        iova_cache_users--;
        if (!iova_cache_users)
                kmem_cache_destroy(iova_cache);
        mutex_unlock(&iova_cache_mutex);
}
EXPORT_SYMBOL_GPL(iova_cache_put);

/**
 * alloc_iova - allocates an iova
 * @iovad: - iova domain in question
 * @size: - size of page frames to allocate
 * @limit_pfn: - max limit address
 * @size_aligned: - set if size_aligned address range is required
 * This function allocates an iova in the range iovad->start_pfn to limit_pfn,
 * searching top-down from limit_pfn to iovad->start_pfn. If the size_aligned
 * flag is set then the allocated address iova->pfn_lo will be naturally
 * aligned on roundup_power_of_two(size).
 */
struct iova *
alloc_iova(struct iova_domain *iovad, unsigned long size,
        unsigned long limit_pfn,
        bool size_aligned)
{
        struct iova *new_iova;
        int ret;

        new_iova = alloc_iova_mem();
        if (!new_iova)
                return NULL;

        ret = __alloc_and_insert_iova_range(iovad, size, limit_pfn + 1,
                        new_iova, size_aligned);

        if (ret) {
                free_iova_mem(new_iova);
                return NULL;
        }

        return new_iova;
}
EXPORT_SYMBOL_GPL(alloc_iova);

static struct iova *
private_find_iova(struct iova_domain *iovad, unsigned long pfn)
{
        struct rb_node *node = iovad->rbroot.rb_node;

        assert_spin_locked(&iovad->iova_rbtree_lock);

        while (node) {
                struct iova *iova = rb_entry(node, struct iova, node);

                /* If pfn falls within iova's range, return iova */
                if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
                        return iova;
                }

                if (pfn < iova->pfn_lo)
                        node = node->rb_left;
                else if (pfn > iova->pfn_lo)
                        node = node->rb_right;
        }

        return NULL;
}

static void private_free_iova(struct iova_domain *iovad, struct iova *iova)
{
        assert_spin_locked(&iovad->iova_rbtree_lock);
        __cached_rbnode_delete_update(iovad, iova);
        rb_erase(&iova->node, &iovad->rbroot);
        free_iova_mem(iova);
}

/**
 * find_iova - finds an iova for a given pfn
 * @iovad: - iova domain in question.
 * @pfn: - page frame number
 * This function finds and returns an iova belonging to the
 * given doamin which matches the given pfn.
 */
struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
{
        unsigned long flags;
        struct iova *iova;

        /* Take the lock so that no other thread is manipulating the rbtree */
        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        iova = private_find_iova(iovad, pfn);
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        return iova;
}
EXPORT_SYMBOL_GPL(find_iova);

/**
 * __free_iova - frees the given iova
 * @iovad: iova domain in question.
 * @iova: iova in question.
 * Frees the given iova belonging to the giving domain
 */
void
__free_iova(struct iova_domain *iovad, struct iova *iova)
{
        unsigned long flags;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        private_free_iova(iovad, iova);
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
}
EXPORT_SYMBOL_GPL(__free_iova);

/**
 * free_iova - finds and frees the iova for a given pfn
 * @iovad: - iova domain in question.
 * @pfn: - pfn that is allocated previously
 * This functions finds an iova for a given pfn and then
 * frees the iova from that domain.
 */
void
free_iova(struct iova_domain *iovad, unsigned long pfn)
{
        struct iova *iova = find_iova(iovad, pfn);

        if (iova)
                __free_iova(iovad, iova);

}
EXPORT_SYMBOL_GPL(free_iova);

/**
 * alloc_iova_fast - allocates an iova from rcache
 * @iovad: - iova domain in question
 * @size: - size of page frames to allocate
 * @limit_pfn: - max limit address
 * This function tries to satisfy an iova allocation from the rcache,
 * and falls back to regular allocation on failure.
*/
unsigned long
alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
                unsigned long limit_pfn)
{
        bool flushed_rcache = false;
        unsigned long iova_pfn;
        struct iova *new_iova;

        iova_pfn = iova_rcache_get(iovad, size, limit_pfn);
        if (iova_pfn)
                return iova_pfn;

retry:
        new_iova = alloc_iova(iovad, size, limit_pfn, true);
        if (!new_iova) {
                unsigned int cpu;

                if (flushed_rcache)
                        return 0;

                /* Try replenishing IOVAs by flushing rcache. */
                flushed_rcache = true;
                for_each_online_cpu(cpu)
                        free_cpu_cached_iovas(cpu, iovad);
                goto retry;
        }

        return new_iova->pfn_lo;
}
EXPORT_SYMBOL_GPL(alloc_iova_fast);

/**
 * free_iova_fast - free iova pfn range into rcache
 * @iovad: - iova domain in question.
 * @pfn: - pfn that is allocated previously
 * @size: - # of pages in range
 * This functions frees an iova range by trying to put it into the rcache,
 * falling back to regular iova deallocation via free_iova() if this fails.
 */
void
free_iova_fast(struct iova_domain *iovad, unsigned long pfn, unsigned long size)
{
        if (iova_rcache_insert(iovad, pfn, size))
                return;

        free_iova(iovad, pfn);
}
EXPORT_SYMBOL_GPL(free_iova_fast);

#define fq_ring_for_each(i, fq) \
        for ((i) = (fq)->head; (i) != (fq)->tail; (i) = ((i) + 1) % IOVA_FQ_SIZE)

static inline bool fq_full(struct iova_fq *fq)
{
        assert_spin_locked(&fq->lock);
        return (((fq->tail + 1) % IOVA_FQ_SIZE) == fq->head);
}

static inline unsigned fq_ring_add(struct iova_fq *fq)
{
        unsigned idx = fq->tail;

        assert_spin_locked(&fq->lock);

        fq->tail = (idx + 1) % IOVA_FQ_SIZE;

        return idx;
}

static void fq_ring_free(struct iova_domain *iovad, struct iova_fq *fq)
{
        u64 counter = atomic64_read(&iovad->fq_flush_finish_cnt);
        unsigned idx;

        assert_spin_locked(&fq->lock);

        fq_ring_for_each(idx, fq) {

                if (fq->entries[idx].counter >= counter)
                        break;

                if (iovad->entry_dtor)
                        iovad->entry_dtor(fq->entries[idx].data);

                free_iova_fast(iovad,
                               fq->entries[idx].iova_pfn,
                               fq->entries[idx].pages);

                fq->head = (fq->head + 1) % IOVA_FQ_SIZE;
        }
}

static void iova_domain_flush(struct iova_domain *iovad)
{
        atomic64_inc(&iovad->fq_flush_start_cnt);
        iovad->flush_cb(iovad);
        atomic64_inc(&iovad->fq_flush_finish_cnt);
}

static void fq_destroy_all_entries(struct iova_domain *iovad)
{
        int cpu;

        /*
         * This code runs when the iova_domain is being detroyed, so don't
         * bother to free iovas, just call the entry_dtor on all remaining
         * entries.
         */
        if (!iovad->entry_dtor)
                return;

        for_each_possible_cpu(cpu) {
                struct iova_fq *fq = per_cpu_ptr(iovad->fq, cpu);
                int idx;

                fq_ring_for_each(idx, fq)
                        iovad->entry_dtor(fq->entries[idx].data);
        }
}

static void fq_flush_timeout(unsigned long data)
{
        struct iova_domain *iovad = (struct iova_domain *)data;
        int cpu;

        atomic_set(&iovad->fq_timer_on, 0);
        iova_domain_flush(iovad);

        for_each_possible_cpu(cpu) {
                unsigned long flags;
                struct iova_fq *fq;

                fq = per_cpu_ptr(iovad->fq, cpu);
                spin_lock_irqsave(&fq->lock, flags);
                fq_ring_free(iovad, fq);
                spin_unlock_irqrestore(&fq->lock, flags);
        }
}

void queue_iova(struct iova_domain *iovad,
                unsigned long pfn, unsigned long pages,
                unsigned long data)
{
        struct iova_fq *fq = get_cpu_ptr(iovad->fq);
        unsigned long flags;
        unsigned idx;

        spin_lock_irqsave(&fq->lock, flags);

        /*
         * First remove all entries from the flush queue that have already been
         * flushed out on another CPU. This makes the fq_full() check below less
         * likely to be true.
         */
        fq_ring_free(iovad, fq);

        if (fq_full(fq)) {
                iova_domain_flush(iovad);
                fq_ring_free(iovad, fq);
        }

        idx = fq_ring_add(fq);

        fq->entries[idx].iova_pfn = pfn;
        fq->entries[idx].pages    = pages;
        fq->entries[idx].data     = data;
        fq->entries[idx].counter  = atomic64_read(&iovad->fq_flush_start_cnt);

        spin_unlock_irqrestore(&fq->lock, flags);

        if (atomic_cmpxchg(&iovad->fq_timer_on, 0, 1) == 0)
                mod_timer(&iovad->fq_timer,
                          jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT));

        put_cpu_ptr(iovad->fq);
}
EXPORT_SYMBOL_GPL(queue_iova);

/**
 * put_iova_domain - destroys the iova doamin
 * @iovad: - iova domain in question.
 * All the iova's in that domain are destroyed.
 */
void put_iova_domain(struct iova_domain *iovad)
{
        struct rb_node *node;
        unsigned long flags;

        free_iova_flush_queue(iovad);
        free_iova_rcaches(iovad);
        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        node = rb_first(&iovad->rbroot);
        while (node) {
                struct iova *iova = rb_entry(node, struct iova, node);

                rb_erase(node, &iovad->rbroot);
                free_iova_mem(iova);
                node = rb_first(&iovad->rbroot);
        }
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
}
EXPORT_SYMBOL_GPL(put_iova_domain);

static int
__is_range_overlap(struct rb_node *node,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct iova *iova = rb_entry(node, struct iova, node);

        if ((pfn_lo <= iova->pfn_hi) && (pfn_hi >= iova->pfn_lo))
                return 1;
        return 0;
}

static inline struct iova *
alloc_and_init_iova(unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct iova *iova;

        iova = alloc_iova_mem();
        if (iova) {
                iova->pfn_lo = pfn_lo;
                iova->pfn_hi = pfn_hi;
        }

        return iova;
}

static struct iova *
__insert_new_range(struct iova_domain *iovad,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct iova *iova;

        iova = alloc_and_init_iova(pfn_lo, pfn_hi);
        if (iova)
                iova_insert_rbtree(&iovad->rbroot, iova, NULL);

        return iova;
}

static void
__adjust_overlap_range(struct iova *iova,
        unsigned long *pfn_lo, unsigned long *pfn_hi)
{
        if (*pfn_lo < iova->pfn_lo)
                iova->pfn_lo = *pfn_lo;
        if (*pfn_hi > iova->pfn_hi)
                *pfn_lo = iova->pfn_hi + 1;
}

/**
 * reserve_iova - reserves an iova in the given range
 * @iovad: - iova domain pointer
 * @pfn_lo: - lower page frame address
 * @pfn_hi:- higher pfn adderss
 * This function allocates reserves the address range from pfn_lo to pfn_hi so
 * that this address is not dished out as part of alloc_iova.
 */
struct iova *
reserve_iova(struct iova_domain *iovad,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct rb_node *node;
        unsigned long flags;
        struct iova *iova;
        unsigned int overlap = 0;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        for (node = rb_first(&iovad->rbroot); node; node = rb_next(node)) {
                if (__is_range_overlap(node, pfn_lo, pfn_hi)) {
                        iova = rb_entry(node, struct iova, node);
                        __adjust_overlap_range(iova, &pfn_lo, &pfn_hi);
                        if ((pfn_lo >= iova->pfn_lo) &&
                                (pfn_hi <= iova->pfn_hi))
                                goto finish;
                        overlap = 1;

                } else if (overlap)
                                break;
        }

        /* We are here either because this is the first reserver node
         * or need to insert remaining non overlap addr range
         */
        iova = __insert_new_range(iovad, pfn_lo, pfn_hi);
finish:

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        return iova;
}
EXPORT_SYMBOL_GPL(reserve_iova);

/**
 * copy_reserved_iova - copies the reserved between domains
 * @from: - source doamin from where to copy
 * @to: - destination domin where to copy
 * This function copies reserved iova's from one doamin to
 * other.
 */
void
copy_reserved_iova(struct iova_domain *from, struct iova_domain *to)
{
        unsigned long flags;
        struct rb_node *node;

        spin_lock_irqsave(&from->iova_rbtree_lock, flags);
        for (node = rb_first(&from->rbroot); node; node = rb_next(node)) {
                struct iova *iova = rb_entry(node, struct iova, node);
                struct iova *new_iova;

                new_iova = reserve_iova(to, iova->pfn_lo, iova->pfn_hi);
                if (!new_iova)
                        printk(KERN_ERR "Reserve iova range %lx@%lx failed\n",
                                iova->pfn_lo, iova->pfn_lo);
        }
        spin_unlock_irqrestore(&from->iova_rbtree_lock, flags);
}
EXPORT_SYMBOL_GPL(copy_reserved_iova);

struct iova *
split_and_remove_iova(struct iova_domain *iovad, struct iova *iova,
                      unsigned long pfn_lo, unsigned long pfn_hi)
{
        unsigned long flags;
        struct iova *prev = NULL, *next = NULL;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        if (iova->pfn_lo < pfn_lo) {
                prev = alloc_and_init_iova(iova->pfn_lo, pfn_lo - 1);
                if (prev == NULL)
                        goto error;
        }
        if (iova->pfn_hi > pfn_hi) {
                next = alloc_and_init_iova(pfn_hi + 1, iova->pfn_hi);
                if (next == NULL)
                        goto error;
        }

        __cached_rbnode_delete_update(iovad, iova);
        rb_erase(&iova->node, &iovad->rbroot);

        if (prev) {
                iova_insert_rbtree(&iovad->rbroot, prev, NULL);
                iova->pfn_lo = pfn_lo;
        }
        if (next) {
                iova_insert_rbtree(&iovad->rbroot, next, NULL);
                iova->pfn_hi = pfn_hi;
        }
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);

        return iova;

error:
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        if (prev)
                free_iova_mem(prev);
        return NULL;
}

/*
 * Magazine caches for IOVA ranges.  For an introduction to magazines,
 * see the USENIX 2001 paper "Magazines and Vmem: Extending the Slab
 * Allocator to Many CPUs and Arbitrary Resources" by Bonwick and Adams.
 * For simplicity, we use a static magazine size and don't implement the
 * dynamic size tuning described in the paper.
 */

#define IOVA_MAG_SIZE 128

struct iova_magazine {
        unsigned long size;
        unsigned long pfns[IOVA_MAG_SIZE];
};

struct iova_cpu_rcache {
        spinlock_t lock;
        struct iova_magazine *loaded;
        struct iova_magazine *prev;
};

static struct iova_magazine *iova_magazine_alloc(gfp_t flags)
{
        return kzalloc(sizeof(struct iova_magazine), flags);
}

static void iova_magazine_free(struct iova_magazine *mag)
{
        kfree(mag);
}

static void
iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
{
        unsigned long flags;
        int i;

        if (!mag)
                return;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);

        for (i = 0 ; i < mag->size; ++i) {
                struct iova *iova = private_find_iova(iovad, mag->pfns[i]);

                BUG_ON(!iova);
                private_free_iova(iovad, iova);
        }

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);

        mag->size = 0;
}

static bool iova_magazine_full(struct iova_magazine *mag)
{
        return (mag && mag->size == IOVA_MAG_SIZE);
}

static bool iova_magazine_empty(struct iova_magazine *mag)
{
        return (!mag || mag->size == 0);
}

static unsigned long iova_magazine_pop(struct iova_magazine *mag,
                                       unsigned long limit_pfn)
{
        BUG_ON(iova_magazine_empty(mag));

        if (mag->pfns[mag->size - 1] >= limit_pfn)
                return 0;

        return mag->pfns[--mag->size];
}

static void iova_magazine_push(struct iova_magazine *mag, unsigned long pfn)
{
        BUG_ON(iova_magazine_full(mag));

        mag->pfns[mag->size++] = pfn;
}

static void init_iova_rcaches(struct iova_domain *iovad)
{
        struct iova_cpu_rcache *cpu_rcache;
        struct iova_rcache *rcache;
        unsigned int cpu;
        int i;

        for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
                rcache = &iovad->rcaches[i];
                spin_lock_init(&rcache->lock);
                rcache->depot_size = 0;
                rcache->cpu_rcaches = __alloc_percpu(sizeof(*cpu_rcache), cache_line_size());
                if (WARN_ON(!rcache->cpu_rcaches))
                        continue;
                for_each_possible_cpu(cpu) {
                        cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
                        spin_lock_init(&cpu_rcache->lock);
                        cpu_rcache->loaded = iova_magazine_alloc(GFP_KERNEL);
                        cpu_rcache->prev = iova_magazine_alloc(GFP_KERNEL);
                }
        }
}

/*
 * Try inserting IOVA range starting with 'iova_pfn' into 'rcache', and
 * return true on success.  Can fail if rcache is full and we can't free
 * space, and free_iova() (our only caller) will then return the IOVA
 * range to the rbtree instead.
 */
static bool __iova_rcache_insert(struct iova_domain *iovad,
                                 struct iova_rcache *rcache,
                                 unsigned long iova_pfn)
{
        struct iova_magazine *mag_to_free = NULL;
        struct iova_cpu_rcache *cpu_rcache;
        bool can_insert = false;
        unsigned long flags;

        cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches);
        spin_lock_irqsave(&cpu_rcache->lock, flags);

        if (!iova_magazine_full(cpu_rcache->loaded)) {
                can_insert = true;
        } else if (!iova_magazine_full(cpu_rcache->prev)) {
                swap(cpu_rcache->prev, cpu_rcache->loaded);
                can_insert = true;
        } else {
                struct iova_magazine *new_mag = iova_magazine_alloc(GFP_ATOMIC);

                if (new_mag) {
                        spin_lock(&rcache->lock);
                        if (rcache->depot_size < MAX_GLOBAL_MAGS) {
                                rcache->depot[rcache->depot_size++] =
                                                cpu_rcache->loaded;
                        } else {
                                mag_to_free = cpu_rcache->loaded;
                        }
                        spin_unlock(&rcache->lock);

                        cpu_rcache->loaded = new_mag;
                        can_insert = true;
                }
        }

        if (can_insert)
                iova_magazine_push(cpu_rcache->loaded, iova_pfn);

        spin_unlock_irqrestore(&cpu_rcache->lock, flags);

        if (mag_to_free) {
                iova_magazine_free_pfns(mag_to_free, iovad);
                iova_magazine_free(mag_to_free);
        }

        return can_insert;
}

static bool iova_rcache_insert(struct iova_domain *iovad, unsigned long pfn,
                               unsigned long size)
{
        unsigned int log_size = order_base_2(size);

        if (log_size >= IOVA_RANGE_CACHE_MAX_SIZE)
                return false;

        return __iova_rcache_insert(iovad, &iovad->rcaches[log_size], pfn);
}

/*
 * Caller wants to allocate a new IOVA range from 'rcache'.  If we can
 * satisfy the request, return a matching non-NULL range and remove
 * it from the 'rcache'.
 */
static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
                                       unsigned long limit_pfn)
{
        struct iova_cpu_rcache *cpu_rcache;
        unsigned long iova_pfn = 0;
        bool has_pfn = false;
        unsigned long flags;

        cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches);
        spin_lock_irqsave(&cpu_rcache->lock, flags);

        if (!iova_magazine_empty(cpu_rcache->loaded)) {
                has_pfn = true;
        } else if (!iova_magazine_empty(cpu_rcache->prev)) {
                swap(cpu_rcache->prev, cpu_rcache->loaded);
                has_pfn = true;
        } else {
                spin_lock(&rcache->lock);
                if (rcache->depot_size > 0) {
                        iova_magazine_free(cpu_rcache->loaded);
                        cpu_rcache->loaded = rcache->depot[--rcache->depot_size];
                        has_pfn = true;
                }
                spin_unlock(&rcache->lock);
        }

        if (has_pfn)
                iova_pfn = iova_magazine_pop(cpu_rcache->loaded, limit_pfn);

        spin_unlock_irqrestore(&cpu_rcache->lock, flags);

        return iova_pfn;
}

/*
 * Try to satisfy IOVA allocation range from rcache.  Fail if requested
 * size is too big or the DMA limit we are given isn't satisfied by the
 * top element in the magazine.
 */
static unsigned long iova_rcache_get(struct iova_domain *iovad,
                                     unsigned long size,
                                     unsigned long limit_pfn)
{
        unsigned int log_size = order_base_2(size);

        if (log_size >= IOVA_RANGE_CACHE_MAX_SIZE)
                return 0;

        return __iova_rcache_get(&iovad->rcaches[log_size], limit_pfn);
}

/*
 * Free a cpu's rcache.
 */
static void free_cpu_iova_rcache(unsigned int cpu, struct iova_domain *iovad,
                                 struct iova_rcache *rcache)
{
        struct iova_cpu_rcache *cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
        unsigned long flags;

        spin_lock_irqsave(&cpu_rcache->lock, flags);

        iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
        iova_magazine_free(cpu_rcache->loaded);

        iova_magazine_free_pfns(cpu_rcache->prev, iovad);
        iova_magazine_free(cpu_rcache->prev);

        spin_unlock_irqrestore(&cpu_rcache->lock, flags);
}

/*
 * free rcache data structures.
 */
static void free_iova_rcaches(struct iova_domain *iovad)
{
        struct iova_rcache *rcache;
        unsigned long flags;
        unsigned int cpu;
        int i, j;

        for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
                rcache = &iovad->rcaches[i];
                for_each_possible_cpu(cpu)
                        free_cpu_iova_rcache(cpu, iovad, rcache);
                spin_lock_irqsave(&rcache->lock, flags);
                free_percpu(rcache->cpu_rcaches);
                for (j = 0; j < rcache->depot_size; ++j) {
                        iova_magazine_free_pfns(rcache->depot[j], iovad);
                        iova_magazine_free(rcache->depot[j]);
                }
                spin_unlock_irqrestore(&rcache->lock, flags);
        }
}

/*
 * free all the IOVA ranges cached by a cpu (used when cpu is unplugged)
 */
void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
{
        struct iova_cpu_rcache *cpu_rcache;
        struct iova_rcache *rcache;
        unsigned long flags;
        int i;

        for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
                rcache = &iovad->rcaches[i];
                cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
                spin_lock_irqsave(&cpu_rcache->lock, flags);
                iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
                iova_magazine_free_pfns(cpu_rcache->prev, iovad);
                spin_unlock_irqrestore(&cpu_rcache->lock, flags);
        }
}

MODULE_AUTHOR("Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>");
MODULE_LICENSE("GPL");