linux/drivers/gpu/drm/ttm/ttm_bo_util.c
Christian König 2ddef17678 drm/ttm: make TT creation purely optional v3
We only need the page array when the BO is about to be accessed.

So not only populate, but also create it on demand.

v2: move NULL check into ttm_tt_create()
v3: fix the occurrence in ttm_bo_kmap_ttm as well

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/373182/
2020-06-29 17:54:13 +02:00

809 lines
19 KiB
C

/* SPDX-License-Identifier: GPL-2.0 OR MIT */
/**************************************************************************
*
* Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sub license, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
/*
* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
*/
#include <drm/ttm/ttm_bo_driver.h>
#include <drm/ttm/ttm_placement.h>
#include <drm/drm_vma_manager.h>
#include <linux/io.h>
#include <linux/highmem.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/module.h>
#include <linux/dma-resv.h>
struct ttm_transfer_obj {
struct ttm_buffer_object base;
struct ttm_buffer_object *bo;
};
void ttm_bo_free_old_node(struct ttm_buffer_object *bo)
{
ttm_bo_mem_put(bo, &bo->mem);
}
int ttm_bo_move_ttm(struct ttm_buffer_object *bo,
struct ttm_operation_ctx *ctx,
struct ttm_mem_reg *new_mem)
{
struct ttm_tt *ttm = bo->ttm;
struct ttm_mem_reg *old_mem = &bo->mem;
int ret;
if (old_mem->mem_type != TTM_PL_SYSTEM) {
ret = ttm_bo_wait(bo, ctx->interruptible, ctx->no_wait_gpu);
if (unlikely(ret != 0)) {
if (ret != -ERESTARTSYS)
pr_err("Failed to expire sync object before unbinding TTM\n");
return ret;
}
ttm_tt_unbind(ttm);
ttm_bo_free_old_node(bo);
ttm_flag_masked(&old_mem->placement, TTM_PL_FLAG_SYSTEM,
TTM_PL_MASK_MEM);
old_mem->mem_type = TTM_PL_SYSTEM;
}
ret = ttm_tt_set_placement_caching(ttm, new_mem->placement);
if (unlikely(ret != 0))
return ret;
if (new_mem->mem_type != TTM_PL_SYSTEM) {
ret = ttm_tt_bind(ttm, new_mem, ctx);
if (unlikely(ret != 0))
return ret;
}
*old_mem = *new_mem;
new_mem->mm_node = NULL;
return 0;
}
EXPORT_SYMBOL(ttm_bo_move_ttm);
int ttm_mem_io_lock(struct ttm_mem_type_manager *man, bool interruptible)
{
if (likely(man->io_reserve_fastpath))
return 0;
if (interruptible)
return mutex_lock_interruptible(&man->io_reserve_mutex);
mutex_lock(&man->io_reserve_mutex);
return 0;
}
void ttm_mem_io_unlock(struct ttm_mem_type_manager *man)
{
if (likely(man->io_reserve_fastpath))
return;
mutex_unlock(&man->io_reserve_mutex);
}
static int ttm_mem_io_evict(struct ttm_mem_type_manager *man)
{
struct ttm_buffer_object *bo;
if (!man->use_io_reserve_lru || list_empty(&man->io_reserve_lru))
return -EAGAIN;
bo = list_first_entry(&man->io_reserve_lru,
struct ttm_buffer_object,
io_reserve_lru);
list_del_init(&bo->io_reserve_lru);
ttm_bo_unmap_virtual_locked(bo);
return 0;
}
int ttm_mem_io_reserve(struct ttm_bo_device *bdev,
struct ttm_mem_reg *mem)
{
struct ttm_mem_type_manager *man = &bdev->man[mem->mem_type];
int ret = 0;
if (!bdev->driver->io_mem_reserve)
return 0;
if (likely(man->io_reserve_fastpath))
return bdev->driver->io_mem_reserve(bdev, mem);
if (bdev->driver->io_mem_reserve &&
mem->bus.io_reserved_count++ == 0) {
retry:
ret = bdev->driver->io_mem_reserve(bdev, mem);
if (ret == -EAGAIN) {
ret = ttm_mem_io_evict(man);
if (ret == 0)
goto retry;
}
}
return ret;
}
void ttm_mem_io_free(struct ttm_bo_device *bdev,
struct ttm_mem_reg *mem)
{
struct ttm_mem_type_manager *man = &bdev->man[mem->mem_type];
if (likely(man->io_reserve_fastpath))
return;
if (bdev->driver->io_mem_reserve &&
--mem->bus.io_reserved_count == 0 &&
bdev->driver->io_mem_free)
bdev->driver->io_mem_free(bdev, mem);
}
int ttm_mem_io_reserve_vm(struct ttm_buffer_object *bo)
{
struct ttm_mem_reg *mem = &bo->mem;
int ret;
if (!mem->bus.io_reserved_vm) {
struct ttm_mem_type_manager *man =
&bo->bdev->man[mem->mem_type];
ret = ttm_mem_io_reserve(bo->bdev, mem);
if (unlikely(ret != 0))
return ret;
mem->bus.io_reserved_vm = true;
if (man->use_io_reserve_lru)
list_add_tail(&bo->io_reserve_lru,
&man->io_reserve_lru);
}
return 0;
}
void ttm_mem_io_free_vm(struct ttm_buffer_object *bo)
{
struct ttm_mem_reg *mem = &bo->mem;
if (mem->bus.io_reserved_vm) {
mem->bus.io_reserved_vm = false;
list_del_init(&bo->io_reserve_lru);
ttm_mem_io_free(bo->bdev, mem);
}
}
static int ttm_mem_reg_ioremap(struct ttm_bo_device *bdev, struct ttm_mem_reg *mem,
void **virtual)
{
struct ttm_mem_type_manager *man = &bdev->man[mem->mem_type];
int ret;
void *addr;
*virtual = NULL;
(void) ttm_mem_io_lock(man, false);
ret = ttm_mem_io_reserve(bdev, mem);
ttm_mem_io_unlock(man);
if (ret || !mem->bus.is_iomem)
return ret;
if (mem->bus.addr) {
addr = mem->bus.addr;
} else {
if (mem->placement & TTM_PL_FLAG_WC)
addr = ioremap_wc(mem->bus.base + mem->bus.offset, mem->bus.size);
else
addr = ioremap(mem->bus.base + mem->bus.offset, mem->bus.size);
if (!addr) {
(void) ttm_mem_io_lock(man, false);
ttm_mem_io_free(bdev, mem);
ttm_mem_io_unlock(man);
return -ENOMEM;
}
}
*virtual = addr;
return 0;
}
static void ttm_mem_reg_iounmap(struct ttm_bo_device *bdev, struct ttm_mem_reg *mem,
void *virtual)
{
struct ttm_mem_type_manager *man;
man = &bdev->man[mem->mem_type];
if (virtual && mem->bus.addr == NULL)
iounmap(virtual);
(void) ttm_mem_io_lock(man, false);
ttm_mem_io_free(bdev, mem);
ttm_mem_io_unlock(man);
}
static int ttm_copy_io_page(void *dst, void *src, unsigned long page)
{
uint32_t *dstP =
(uint32_t *) ((unsigned long)dst + (page << PAGE_SHIFT));
uint32_t *srcP =
(uint32_t *) ((unsigned long)src + (page << PAGE_SHIFT));
int i;
for (i = 0; i < PAGE_SIZE / sizeof(uint32_t); ++i)
iowrite32(ioread32(srcP++), dstP++);
return 0;
}
static int ttm_copy_io_ttm_page(struct ttm_tt *ttm, void *src,
unsigned long page,
pgprot_t prot)
{
struct page *d = ttm->pages[page];
void *dst;
if (!d)
return -ENOMEM;
src = (void *)((unsigned long)src + (page << PAGE_SHIFT));
dst = kmap_atomic_prot(d, prot);
if (!dst)
return -ENOMEM;
memcpy_fromio(dst, src, PAGE_SIZE);
kunmap_atomic(dst);
return 0;
}
static int ttm_copy_ttm_io_page(struct ttm_tt *ttm, void *dst,
unsigned long page,
pgprot_t prot)
{
struct page *s = ttm->pages[page];
void *src;
if (!s)
return -ENOMEM;
dst = (void *)((unsigned long)dst + (page << PAGE_SHIFT));
src = kmap_atomic_prot(s, prot);
if (!src)
return -ENOMEM;
memcpy_toio(dst, src, PAGE_SIZE);
kunmap_atomic(src);
return 0;
}
int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
struct ttm_operation_ctx *ctx,
struct ttm_mem_reg *new_mem)
{
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_mem_type_manager *man = &bdev->man[new_mem->mem_type];
struct ttm_tt *ttm = bo->ttm;
struct ttm_mem_reg *old_mem = &bo->mem;
struct ttm_mem_reg old_copy = *old_mem;
void *old_iomap;
void *new_iomap;
int ret;
unsigned long i;
unsigned long page;
unsigned long add = 0;
int dir;
ret = ttm_bo_wait(bo, ctx->interruptible, ctx->no_wait_gpu);
if (ret)
return ret;
ret = ttm_mem_reg_ioremap(bdev, old_mem, &old_iomap);
if (ret)
return ret;
ret = ttm_mem_reg_ioremap(bdev, new_mem, &new_iomap);
if (ret)
goto out;
/*
* Single TTM move. NOP.
*/
if (old_iomap == NULL && new_iomap == NULL)
goto out2;
/*
* Don't move nonexistent data. Clear destination instead.
*/
if (old_iomap == NULL &&
(ttm == NULL || (ttm->state == tt_unpopulated &&
!(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)))) {
memset_io(new_iomap, 0, new_mem->num_pages*PAGE_SIZE);
goto out2;
}
/*
* TTM might be null for moves within the same region.
*/
if (ttm) {
ret = ttm_tt_populate(ttm, ctx);
if (ret)
goto out1;
}
add = 0;
dir = 1;
if ((old_mem->mem_type == new_mem->mem_type) &&
(new_mem->start < old_mem->start + old_mem->size)) {
dir = -1;
add = new_mem->num_pages - 1;
}
for (i = 0; i < new_mem->num_pages; ++i) {
page = i * dir + add;
if (old_iomap == NULL) {
pgprot_t prot = ttm_io_prot(old_mem->placement,
PAGE_KERNEL);
ret = ttm_copy_ttm_io_page(ttm, new_iomap, page,
prot);
} else if (new_iomap == NULL) {
pgprot_t prot = ttm_io_prot(new_mem->placement,
PAGE_KERNEL);
ret = ttm_copy_io_ttm_page(ttm, old_iomap, page,
prot);
} else {
ret = ttm_copy_io_page(new_iomap, old_iomap, page);
}
if (ret)
goto out1;
}
mb();
out2:
old_copy = *old_mem;
*old_mem = *new_mem;
new_mem->mm_node = NULL;
if (man->flags & TTM_MEMTYPE_FLAG_FIXED) {
ttm_tt_destroy(ttm);
bo->ttm = NULL;
}
out1:
ttm_mem_reg_iounmap(bdev, old_mem, new_iomap);
out:
ttm_mem_reg_iounmap(bdev, &old_copy, old_iomap);
/*
* On error, keep the mm node!
*/
if (!ret)
ttm_bo_mem_put(bo, &old_copy);
return ret;
}
EXPORT_SYMBOL(ttm_bo_move_memcpy);
static void ttm_transfered_destroy(struct ttm_buffer_object *bo)
{
struct ttm_transfer_obj *fbo;
fbo = container_of(bo, struct ttm_transfer_obj, base);
ttm_bo_put(fbo->bo);
kfree(fbo);
}
/**
* ttm_buffer_object_transfer
*
* @bo: A pointer to a struct ttm_buffer_object.
* @new_obj: A pointer to a pointer to a newly created ttm_buffer_object,
* holding the data of @bo with the old placement.
*
* This is a utility function that may be called after an accelerated move
* has been scheduled. A new buffer object is created as a placeholder for
* the old data while it's being copied. When that buffer object is idle,
* it can be destroyed, releasing the space of the old placement.
* Returns:
* !0: Failure.
*/
static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
struct ttm_buffer_object **new_obj)
{
struct ttm_transfer_obj *fbo;
int ret;
fbo = kmalloc(sizeof(*fbo), GFP_KERNEL);
if (!fbo)
return -ENOMEM;
fbo->base = *bo;
fbo->base.mem.placement |= TTM_PL_FLAG_NO_EVICT;
ttm_bo_get(bo);
fbo->bo = bo;
/**
* Fix up members that we shouldn't copy directly:
* TODO: Explicit member copy would probably be better here.
*/
atomic_inc(&ttm_bo_glob.bo_count);
INIT_LIST_HEAD(&fbo->base.ddestroy);
INIT_LIST_HEAD(&fbo->base.lru);
INIT_LIST_HEAD(&fbo->base.swap);
INIT_LIST_HEAD(&fbo->base.io_reserve_lru);
fbo->base.moving = NULL;
drm_vma_node_reset(&fbo->base.base.vma_node);
kref_init(&fbo->base.kref);
fbo->base.destroy = &ttm_transfered_destroy;
fbo->base.acc_size = 0;
if (bo->type != ttm_bo_type_sg)
fbo->base.base.resv = &fbo->base.base._resv;
dma_resv_init(&fbo->base.base._resv);
fbo->base.base.dev = NULL;
ret = dma_resv_trylock(&fbo->base.base._resv);
WARN_ON(!ret);
*new_obj = &fbo->base;
return 0;
}
pgprot_t ttm_io_prot(uint32_t caching_flags, pgprot_t tmp)
{
/* Cached mappings need no adjustment */
if (caching_flags & TTM_PL_FLAG_CACHED)
return tmp;
#if defined(__i386__) || defined(__x86_64__)
if (caching_flags & TTM_PL_FLAG_WC)
tmp = pgprot_writecombine(tmp);
else if (boot_cpu_data.x86 > 3)
tmp = pgprot_noncached(tmp);
#endif
#if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
defined(__powerpc__) || defined(__mips__)
if (caching_flags & TTM_PL_FLAG_WC)
tmp = pgprot_writecombine(tmp);
else
tmp = pgprot_noncached(tmp);
#endif
#if defined(__sparc__)
tmp = pgprot_noncached(tmp);
#endif
return tmp;
}
EXPORT_SYMBOL(ttm_io_prot);
static int ttm_bo_ioremap(struct ttm_buffer_object *bo,
unsigned long offset,
unsigned long size,
struct ttm_bo_kmap_obj *map)
{
struct ttm_mem_reg *mem = &bo->mem;
if (bo->mem.bus.addr) {
map->bo_kmap_type = ttm_bo_map_premapped;
map->virtual = (void *)(((u8 *)bo->mem.bus.addr) + offset);
} else {
map->bo_kmap_type = ttm_bo_map_iomap;
if (mem->placement & TTM_PL_FLAG_WC)
map->virtual = ioremap_wc(bo->mem.bus.base + bo->mem.bus.offset + offset,
size);
else
map->virtual = ioremap(bo->mem.bus.base + bo->mem.bus.offset + offset,
size);
}
return (!map->virtual) ? -ENOMEM : 0;
}
static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
unsigned long start_page,
unsigned long num_pages,
struct ttm_bo_kmap_obj *map)
{
struct ttm_mem_reg *mem = &bo->mem;
struct ttm_operation_ctx ctx = {
.interruptible = false,
.no_wait_gpu = false
};
struct ttm_tt *ttm;
pgprot_t prot;
int ret;
ret = ttm_tt_create(bo, true);
if (ret)
return ret;
ttm = bo->ttm;
ret = ttm_tt_populate(ttm, &ctx);
if (ret)
return ret;
if (num_pages == 1 && (mem->placement & TTM_PL_FLAG_CACHED)) {
/*
* We're mapping a single page, and the desired
* page protection is consistent with the bo.
*/
map->bo_kmap_type = ttm_bo_map_kmap;
map->page = ttm->pages[start_page];
map->virtual = kmap(map->page);
} else {
/*
* We need to use vmap to get the desired page protection
* or to make the buffer object look contiguous.
*/
prot = ttm_io_prot(mem->placement, PAGE_KERNEL);
map->bo_kmap_type = ttm_bo_map_vmap;
map->virtual = vmap(ttm->pages + start_page, num_pages,
0, prot);
}
return (!map->virtual) ? -ENOMEM : 0;
}
int ttm_bo_kmap(struct ttm_buffer_object *bo,
unsigned long start_page, unsigned long num_pages,
struct ttm_bo_kmap_obj *map)
{
struct ttm_mem_type_manager *man =
&bo->bdev->man[bo->mem.mem_type];
unsigned long offset, size;
int ret;
map->virtual = NULL;
map->bo = bo;
if (num_pages > bo->num_pages)
return -EINVAL;
if (start_page > bo->num_pages)
return -EINVAL;
(void) ttm_mem_io_lock(man, false);
ret = ttm_mem_io_reserve(bo->bdev, &bo->mem);
ttm_mem_io_unlock(man);
if (ret)
return ret;
if (!bo->mem.bus.is_iomem) {
return ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
} else {
offset = start_page << PAGE_SHIFT;
size = num_pages << PAGE_SHIFT;
return ttm_bo_ioremap(bo, offset, size, map);
}
}
EXPORT_SYMBOL(ttm_bo_kmap);
void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
{
struct ttm_buffer_object *bo = map->bo;
struct ttm_mem_type_manager *man =
&bo->bdev->man[bo->mem.mem_type];
if (!map->virtual)
return;
switch (map->bo_kmap_type) {
case ttm_bo_map_iomap:
iounmap(map->virtual);
break;
case ttm_bo_map_vmap:
vunmap(map->virtual);
break;
case ttm_bo_map_kmap:
kunmap(map->page);
break;
case ttm_bo_map_premapped:
break;
default:
BUG();
}
(void) ttm_mem_io_lock(man, false);
ttm_mem_io_free(map->bo->bdev, &map->bo->mem);
ttm_mem_io_unlock(man);
map->virtual = NULL;
map->page = NULL;
}
EXPORT_SYMBOL(ttm_bo_kunmap);
int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
struct dma_fence *fence,
bool evict,
struct ttm_mem_reg *new_mem)
{
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_mem_type_manager *man = &bdev->man[new_mem->mem_type];
struct ttm_mem_reg *old_mem = &bo->mem;
int ret;
struct ttm_buffer_object *ghost_obj;
dma_resv_add_excl_fence(bo->base.resv, fence);
if (evict) {
ret = ttm_bo_wait(bo, false, false);
if (ret)
return ret;
if (man->flags & TTM_MEMTYPE_FLAG_FIXED) {
ttm_tt_destroy(bo->ttm);
bo->ttm = NULL;
}
ttm_bo_free_old_node(bo);
} else {
/**
* This should help pipeline ordinary buffer moves.
*
* Hang old buffer memory on a new buffer object,
* and leave it to be released when the GPU
* operation has completed.
*/
dma_fence_put(bo->moving);
bo->moving = dma_fence_get(fence);
ret = ttm_buffer_object_transfer(bo, &ghost_obj);
if (ret)
return ret;
dma_resv_add_excl_fence(&ghost_obj->base._resv, fence);
/**
* If we're not moving to fixed memory, the TTM object
* needs to stay alive. Otherwhise hang it on the ghost
* bo to be unbound and destroyed.
*/
if (!(man->flags & TTM_MEMTYPE_FLAG_FIXED))
ghost_obj->ttm = NULL;
else
bo->ttm = NULL;
dma_resv_unlock(&ghost_obj->base._resv);
ttm_bo_put(ghost_obj);
}
*old_mem = *new_mem;
new_mem->mm_node = NULL;
return 0;
}
EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
int ttm_bo_pipeline_move(struct ttm_buffer_object *bo,
struct dma_fence *fence, bool evict,
struct ttm_mem_reg *new_mem)
{
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_mem_reg *old_mem = &bo->mem;
struct ttm_mem_type_manager *from = &bdev->man[old_mem->mem_type];
struct ttm_mem_type_manager *to = &bdev->man[new_mem->mem_type];
int ret;
dma_resv_add_excl_fence(bo->base.resv, fence);
if (!evict) {
struct ttm_buffer_object *ghost_obj;
/**
* This should help pipeline ordinary buffer moves.
*
* Hang old buffer memory on a new buffer object,
* and leave it to be released when the GPU
* operation has completed.
*/
dma_fence_put(bo->moving);
bo->moving = dma_fence_get(fence);
ret = ttm_buffer_object_transfer(bo, &ghost_obj);
if (ret)
return ret;
dma_resv_add_excl_fence(&ghost_obj->base._resv, fence);
/**
* If we're not moving to fixed memory, the TTM object
* needs to stay alive. Otherwhise hang it on the ghost
* bo to be unbound and destroyed.
*/
if (!(to->flags & TTM_MEMTYPE_FLAG_FIXED))
ghost_obj->ttm = NULL;
else
bo->ttm = NULL;
dma_resv_unlock(&ghost_obj->base._resv);
ttm_bo_put(ghost_obj);
} else if (from->flags & TTM_MEMTYPE_FLAG_FIXED) {
/**
* BO doesn't have a TTM we need to bind/unbind. Just remember
* this eviction and free up the allocation
*/
spin_lock(&from->move_lock);
if (!from->move || dma_fence_is_later(fence, from->move)) {
dma_fence_put(from->move);
from->move = dma_fence_get(fence);
}
spin_unlock(&from->move_lock);
ttm_bo_free_old_node(bo);
dma_fence_put(bo->moving);
bo->moving = dma_fence_get(fence);
} else {
/**
* Last resort, wait for the move to be completed.
*
* Should never happen in pratice.
*/
ret = ttm_bo_wait(bo, false, false);
if (ret)
return ret;
if (to->flags & TTM_MEMTYPE_FLAG_FIXED) {
ttm_tt_destroy(bo->ttm);
bo->ttm = NULL;
}
ttm_bo_free_old_node(bo);
}
*old_mem = *new_mem;
new_mem->mm_node = NULL;
return 0;
}
EXPORT_SYMBOL(ttm_bo_pipeline_move);
int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo)
{
struct ttm_buffer_object *ghost;
int ret;
ret = ttm_buffer_object_transfer(bo, &ghost);
if (ret)
return ret;
ret = dma_resv_copy_fences(&ghost->base._resv, bo->base.resv);
/* Last resort, wait for the BO to be idle when we are OOM */
if (ret)
ttm_bo_wait(bo, false, false);
memset(&bo->mem, 0, sizeof(bo->mem));
bo->mem.mem_type = TTM_PL_SYSTEM;
bo->ttm = NULL;
dma_resv_unlock(&ghost->base._resv);
ttm_bo_put(ghost);
return 0;
}