iova.c

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/*
 * 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 <[email protected]>
 */

#include <linux/iova.h>

void
init_iova_domain(struct iova_domain *iovad, unsigned long pfn_32bit)
{
    spin_lock_init(&iovad->iova_rbtree_lock);
    iovad->rbroot = RB_ROOT;
    iovad->cached32_node = NULL;
    iovad->dma_32bit_pfn = pfn_32bit;
}

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 =
            container_of(iovad->cached32_node, struct iova, node);
        *limit_pfn = curr_iova->pfn_lo - 1;
        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 = container_of(curr, struct iova, node);

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

/* Computes the padding size required, to make the
 * the start address naturally aligned on its size
 */
static int
iova_get_pad_size(int size, unsigned int limit_pfn)
{
    unsigned int pad_size = 0;
    unsigned int order = ilog2(size);

    if (order)
        pad_size = (limit_pfn + 1) % (1 << order);

    return pad_size;
}

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 = container_of(curr, struct iova, node);

        if (limit_pfn < curr_iova->pfn_lo)
            goto move_left;
        else if (limit_pfn < curr_iova->pfn_hi)
            goto adjust_limit_pfn;
        else {
            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 */
        }
adjust_limit_pfn:
        limit_pfn = curr_iova->pfn_lo - 1;
move_left:
        prev = curr;
        curr = rb_prev(curr);
    }

    if (!curr) {
        if (size_aligned)
            pad_size = iova_get_pad_size(size, limit_pfn);
        if ((IOVA_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) + 1;
    new->pfn_hi = new->pfn_lo + size - 1;

    /* Insert the new_iova into domain rbtree by holding writer lock */
    /* Add new node and rebalance tree. */
    {
        struct rb_node **entry, *parent = NULL;

        /* If we have 'prev', it's a valid place to start the
           insertion. Otherwise, start from the root. */
        if (prev)
            entry = &prev;
        else
            entry = &iovad->rbroot.rb_node;

        /* Figure out where to put new node */
        while (*entry) {
            struct iova *this = container_of(*entry,
                            struct iova, node);
            parent = *entry;

            if (new->pfn_lo < this->pfn_lo)
                entry = &((*entry)->rb_left);
            else if (new->pfn_lo > this->pfn_lo)
                entry = &((*entry)->rb_right);
            else
                BUG(); /* this should not happen */
        }

        /* Add new node and rebalance tree. */
        rb_link_node(&new->node, parent, entry);
        rb_insert_color(&new->node, &iovad->rbroot);
    }
    __cached_rbnode_insert_update(iovad, saved_pfn, new);

    spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);


    return 0;
}

static void
iova_insert_rbtree(struct rb_root *root, struct iova *iova)
{
    struct rb_node **new = &(root->rb_node), *parent = NULL;
    /* Figure out where to put new node */
    while (*new) {
        struct iova *this = container_of(*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
            BUG(); /* this should not happen */
    }
    /* Add new node and rebalance tree. */
    rb_link_node(&iova->node, parent, new);
    rb_insert_color(&iova->node, root);
}

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;

    /* If size aligned is set then round the size to
     * to next power of two.
     */
    if (size_aligned)
        size = __roundup_pow_of_two(size);

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

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

    return new_iova;
}

struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
{
    unsigned long flags;
    struct rb_node *node;

    /* Take the lock so that no other thread is manipulating the rbtree */
    spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
    node = iovad->rbroot.rb_node;
    while (node) {
        struct iova *iova = container_of(node, struct iova, node);

        /* If pfn falls within iova's range, return iova */
        if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
            spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
            /* We are not holding the lock while this iova
             * is referenced by the caller as the same thread
             * which called this function also calls __free_iova()
             * and it is by design that only one thread can possibly
             * reference a particular iova and hence no conflict.
             */
            return iova;
        }

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

    spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
    return NULL;
}

void
__free_iova(struct iova_domain *iovad, struct iova *iova)
{
    unsigned long flags;

    spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
    __cached_rbnode_delete_update(iovad, iova);
    rb_erase(&iova->node, &iovad->rbroot);
    spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
    free_iova_mem(iova);
}

void
free_iova(struct iova_domain *iovad, unsigned long pfn)
{
    struct iova *iova = find_iova(iovad, pfn);
    if (iova)
        __free_iova(iovad, iova);

}

void put_iova_domain(struct iova_domain *iovad)
{
    struct rb_node *node;
    unsigned long flags;

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

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

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

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

    iova = alloc_iova_mem();
    if (!iova)
        return iova;

    iova->pfn_hi = pfn_hi;
    iova->pfn_lo = pfn_lo;
    iova_insert_rbtree(&iovad->rbroot, iova);
    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;
}

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 = container_of(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;
}

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 = container_of(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);
}