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drm/i915: Fix lock order reversal in GTT pwrite path.

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Since the pagefault path determines that the lock order we use has to be
mmap_sem -> struct_mutex, we can't allow page faults to occur while the
struct_mutex is held.  To fix this in pwrite, we first try optimistically to
see if we can copy from user without faulting.  If it fails, fall back to
using get_user_pages to pin the user's memory, and map those pages
atomically when copying it to the GPU.

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This commit is contained in:
Eric Anholt 2009-03-09 09:42:23 -07:00
parent 13520b051e
commit 3de09aa3b3
1 changed files with 139 additions and 27 deletions
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166
drivers/gpu/drm/i915/i915_gem.c
View file

@ -223,29 +223,34 @@ fast_user_write(struct io_mapping *mapping,
*/
static inline int
slow_user_write(struct io_mapping *mapping,
loff_t page_base, int page_offset,
char __user *user_data,
int length)
slow_kernel_write(struct io_mapping *mapping,
loff_t gtt_base, int gtt_offset,
struct page *user_page, int user_offset,
int length)
{
char __iomem *vaddr;
char *src_vaddr, *dst_vaddr;
unsigned long unwritten;
vaddr = io_mapping_map_wc(mapping, page_base);
if (vaddr == NULL)
return -EFAULT;
unwritten = __copy_from_user(vaddr + page_offset,
user_data, length);
io_mapping_unmap(vaddr);
dst_vaddr = io_mapping_map_atomic_wc(mapping, gtt_base);
src_vaddr = kmap_atomic(user_page, KM_USER1);
unwritten = __copy_from_user_inatomic_nocache(dst_vaddr + gtt_offset,
src_vaddr + user_offset,
length);
kunmap_atomic(src_vaddr, KM_USER1);
io_mapping_unmap_atomic(dst_vaddr);
if (unwritten)
return -EFAULT;
return 0;
}
/**
* This is the fast pwrite path, where we copy the data directly from the
* user into the GTT, uncached.
*/
static int
i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
struct drm_i915_gem_pwrite *args,
struct drm_file *file_priv)
i915_gem_gtt_pwrite_fast(struct drm_device *dev, struct drm_gem_object *obj,
struct drm_i915_gem_pwrite *args,
struct drm_file *file_priv)
{
struct drm_i915_gem_object *obj_priv = obj->driver_private;
drm_i915_private_t *dev_priv = dev->dev_private;
@ -273,7 +278,6 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
obj_priv = obj->driver_private;
offset = obj_priv->gtt_offset + args->offset;
obj_priv->dirty = 1;
while (remain > 0) {
/* Operation in this page
@ -292,16 +296,11 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
page_offset, user_data, page_length);
/* If we get a fault while copying data, then (presumably) our
* source page isn't available. In this case, use the
* non-atomic function
* source page isn't available. Return the error and we'll
* retry in the slow path.
*/
if (ret) {
ret = slow_user_write (dev_priv->mm.gtt_mapping,
page_base, page_offset,
user_data, page_length);
if (ret)
goto fail;
}
if (ret)
goto fail;
remain -= page_length;
user_data += page_length;
@ -315,6 +314,115 @@ fail:
return ret;
}
/**
* This is the fallback GTT pwrite path, which uses get_user_pages to pin
* the memory and maps it using kmap_atomic for copying.
*
* This code resulted in x11perf -rgb10text consuming about 10% more CPU
* than using i915_gem_gtt_pwrite_fast on a G45 (32-bit).
*/
static int
i915_gem_gtt_pwrite_slow(struct drm_device *dev, struct drm_gem_object *obj,
struct drm_i915_gem_pwrite *args,
struct drm_file *file_priv)
{
struct drm_i915_gem_object *obj_priv = obj->driver_private;
drm_i915_private_t *dev_priv = dev->dev_private;
ssize_t remain;
loff_t gtt_page_base, offset;
loff_t first_data_page, last_data_page, num_pages;
loff_t pinned_pages, i;
struct page **user_pages;
struct mm_struct *mm = current->mm;
int gtt_page_offset, data_page_offset, data_page_index, page_length;
int ret;
uint64_t data_ptr = args->data_ptr;
remain = args->size;
/* Pin the user pages containing the data. We can't fault while
* holding the struct mutex, and all of the pwrite implementations
* want to hold it while dereferencing the user data.
*/
first_data_page = data_ptr / PAGE_SIZE;
last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
num_pages = last_data_page - first_data_page + 1;
user_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
if (user_pages == NULL)
return -ENOMEM;
down_read(&mm->mmap_sem);
pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
num_pages, 0, 0, user_pages, NULL);
up_read(&mm->mmap_sem);
if (pinned_pages < num_pages) {
ret = -EFAULT;
goto out_unpin_pages;
}
mutex_lock(&dev->struct_mutex);
ret = i915_gem_object_pin(obj, 0);
if (ret)
goto out_unlock;
ret = i915_gem_object_set_to_gtt_domain(obj, 1);
if (ret)
goto out_unpin_object;
obj_priv = obj->driver_private;
offset = obj_priv->gtt_offset + args->offset;
while (remain > 0) {
/* Operation in this page
*
* gtt_page_base = page offset within aperture
* gtt_page_offset = offset within page in aperture
* data_page_index = page number in get_user_pages return
* data_page_offset = offset with data_page_index page.
* page_length = bytes to copy for this page
*/
gtt_page_base = offset & PAGE_MASK;
gtt_page_offset = offset & ~PAGE_MASK;
data_page_index = data_ptr / PAGE_SIZE - first_data_page;
data_page_offset = data_ptr & ~PAGE_MASK;
page_length = remain;
if ((gtt_page_offset + page_length) > PAGE_SIZE)
page_length = PAGE_SIZE - gtt_page_offset;
if ((data_page_offset + page_length) > PAGE_SIZE)
page_length = PAGE_SIZE - data_page_offset;
ret = slow_kernel_write(dev_priv->mm.gtt_mapping,
gtt_page_base, gtt_page_offset,
user_pages[data_page_index],
data_page_offset,
page_length);
/* If we get a fault while copying data, then (presumably) our
* source page isn't available. Return the error and we'll
* retry in the slow path.
*/
if (ret)
goto out_unpin_object;
remain -= page_length;
offset += page_length;
data_ptr += page_length;
}
out_unpin_object:
i915_gem_object_unpin(obj);
out_unlock:
mutex_unlock(&dev->struct_mutex);
out_unpin_pages:
for (i = 0; i < pinned_pages; i++)
page_cache_release(user_pages[i]);
kfree(user_pages);
return ret;
}
static int
i915_gem_shmem_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
struct drm_i915_gem_pwrite *args,
@ -388,9 +496,13 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
if (obj_priv->phys_obj)
ret = i915_gem_phys_pwrite(dev, obj, args, file_priv);
else if (obj_priv->tiling_mode == I915_TILING_NONE &&
dev->gtt_total != 0)
ret = i915_gem_gtt_pwrite(dev, obj, args, file_priv);
else
dev->gtt_total != 0) {
ret = i915_gem_gtt_pwrite_fast(dev, obj, args, file_priv);
if (ret == -EFAULT) {
ret = i915_gem_gtt_pwrite_slow(dev, obj, args,
file_priv);
}
} else
ret = i915_gem_shmem_pwrite(dev, obj, args, file_priv);
#if WATCH_PWRITE