[PATCH 03/13] drm/i915: rewrite shmem_pread_slow to use copy_to_user

Daniel Vetter
2011-11-06T19:13:50Z

Like for shmem_pwrite_slow. The only difference is that because we
read data, we can leave the fetched cachelines in the cpu: In the case
that the object isn't in the cpu read domain anymore, the clflush for
the next cpu read domain invalidation will simply drop these
cachelines.

slow_shmem_bit17_copy is now ununsed, so kill it.

With this patch tests/gem_mmap_gtt now actually works.

v2: add __ to copy_to_user_swizzled as suggested by Chris Wilson.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38115
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem.c | 172 +++++++++++++--------------------------
1 files changed, 56 insertions(+), 116 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f9efebb..be1dd4f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -277,55 +277,6 @@ slow_shmem_copy(struct page *dst_page,
kunmap(dst_page);
}

-static inline void
-slow_shmem_bit17_copy(struct page *gpu_page,
- int gpu_offset,
- struct page *cpu_page,
- int cpu_offset,
- int length,
- int is_read)
-{
- char *gpu_vaddr, *cpu_vaddr;
-
- /* Use the unswizzled path if this page isn't affected. */
- if ((page_to_phys(gpu_page) & (1 << 17)) == 0) {
- if (is_read)
- return slow_shmem_copy(cpu_page, cpu_offset,
- gpu_page, gpu_offset, length);
- else
- return slow_shmem_copy(gpu_page, gpu_offset,
- cpu_page, cpu_offset, length);
- }
-
- gpu_vaddr = kmap(gpu_page);
- cpu_vaddr = kmap(cpu_page);
-
- /* Copy the data, XORing A6 with A17 (1). The user already knows he's
- * XORing with the other bits (A9 for Y, A9 and A10 for X)
- */
- while (length > 0) {
- int cacheline_end = ALIGN(gpu_offset + 1, 64);
- int this_length = min(cacheline_end - gpu_offset, length);
- int swizzled_gpu_offset = gpu_offset ^ 64;
-
- if (is_read) {
- memcpy(cpu_vaddr + cpu_offset,
- gpu_vaddr + swizzled_gpu_offset,
- this_length);
- } else {
- memcpy(gpu_vaddr + swizzled_gpu_offset,
- cpu_vaddr + cpu_offset,
- this_length);
- }
- cpu_offset += this_length;
- gpu_offset += this_length;
- length -= this_length;
- }
-
- kunmap(cpu_page);
- kunmap(gpu_page);
-}
-
/**
* This is the fast shmem pread path, which attempts to copy_from_user directly
* from the backing pages of the object to the user's address space. On a
@@ -387,6 +338,32 @@ i915_gem_shmem_pread_fast(struct drm_device *dev,
}

static inline int
+__copy_to_user_swizzled(char __user *cpu_vaddr,
+ const char *gpu_vaddr, int gpu_offset,
+ int length)
+{
+ int ret, cpu_offset = 0;
+
+ while (length > 0) {
+ int cacheline_end = ALIGN(gpu_offset + 1, 64);
+ int this_length = min(cacheline_end - gpu_offset, length);
+ int swizzled_gpu_offset = gpu_offset ^ 64;
+
+ ret = __copy_to_user(cpu_vaddr + cpu_offset,
+ gpu_vaddr + swizzled_gpu_offset,
+ this_length);
+ if (ret)
+ return ret + length;
+
+ cpu_offset += this_length;
+ gpu_offset += this_length;
+ length -= this_length;
+ }
+
+ return 0;
+}
+
+static inline int
__copy_from_user_swizzled(char __user *gpu_vaddr, int gpu_offset,
const char *cpu_vaddr,
int length)
@@ -425,72 +402,34 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
struct drm_file *file)
{
struct address_space *mapping = obj->base.filp->f_path.dentry->d_inode->i_mapping;
- struct mm_struct *mm = current->mm;
- struct page **user_pages;
+ char __user *user_data;
ssize_t remain;
- loff_t offset, pinned_pages, i;
- loff_t first_data_page, last_data_page, num_pages;
- int shmem_page_offset;
- int data_page_index, data_page_offset;
- int page_length;
- int ret;
- uint64_t data_ptr = args->data_ptr;
- int do_bit17_swizzling;
+ loff_t offset;
+ int shmem_page_offset, page_length, ret;
+ int obj_do_bit17_swizzling, page_do_bit17_swizzling;

+ user_data = (char __user *) (uintptr_t) args->data_ptr;
remain = args->size;

- /* Pin the user pages containing the data. We can't fault while
- * holding the struct mutex, yet we 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;
+ obj_do_bit17_swizzling = i915_gem_object_needs_bit17_swizzle(obj);

- user_pages = drm_malloc_ab(num_pages, sizeof(struct page *));
- if (user_pages == NULL)
- return -ENOMEM;
+ offset = args->offset;

mutex_unlock(&dev->struct_mutex);
- down_read(&mm->mmap_sem);
- pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
- num_pages, 1, 0, user_pages, NULL);
- up_read(&mm->mmap_sem);
- mutex_lock(&dev->struct_mutex);
- if (pinned_pages < num_pages) {
- ret = -EFAULT;
- goto out;
- }
-
- ret = i915_gem_object_set_cpu_read_domain_range(obj,
- args->offset,
- args->size);
- if (ret)
- goto out;
-
- do_bit17_swizzling = i915_gem_object_needs_bit17_swizzle(obj);
-
- offset = args->offset;

while (remain > 0) {
struct page *page;
+ char *vaddr;

/* Operation in this page
*
* shmem_page_offset = offset within page in shmem file
- * 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
*/
shmem_page_offset = offset_in_page(offset);
- data_page_index = data_ptr / PAGE_SIZE - first_data_page;
- data_page_offset = offset_in_page(data_ptr);
-
page_length = remain;
if ((shmem_page_offset + page_length) > PAGE_SIZE)
page_length = PAGE_SIZE - shmem_page_offset;
- if ((data_page_offset + page_length) > PAGE_SIZE)
- page_length = PAGE_SIZE - data_page_offset;

page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
if (IS_ERR(page)) {
@@ -498,36 +437,37 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
goto out;
}

- if (do_bit17_swizzling) {
- slow_shmem_bit17_copy(page,
- shmem_page_offset,
- user_pages[data_page_index],
- data_page_offset,
- page_length,
- 1);
- } else {
- slow_shmem_copy(user_pages[data_page_index],
- data_page_offset,
- page,
- shmem_page_offset,
- page_length);
- }
+ page_do_bit17_swizzling = (page_to_phys(page) & (1 << 17)) == 0;
+
+ vaddr = kmap(page);
+ if (obj_do_bit17_swizzling && page_do_bit17_swizzling)
+ ret = __copy_to_user_swizzled(user_data,
+ vaddr, shmem_page_offset,
+ page_length);
+ else
+ ret = __copy_to_user(user_data,
+ vaddr + shmem_page_offset,
+ page_length);
+ kunmap(page);

mark_page_accessed(page);
page_cache_release(page);

+ if (ret) {
+ ret = -EFAULT;
+ goto out;
+ }
+
remain -= page_length;
- data_ptr += page_length;
+ user_data += page_length;
offset += page_length;
}

out:
- for (i = 0; i < pinned_pages; i++) {
- SetPageDirty(user_pages[i]);
- mark_page_accessed(user_pages[i]);
- page_cache_release(user_pages[i]);
- }
- drm_free_large(user_pages);
+ mutex_lock(&dev->struct_mutex);
+ /* Fixup: Kill any reinstated backing storage pages */
+ if (obj->madv == __I915_MADV_PURGED)
+ i915_gem_object_truncate(obj);

return ret;
}
--
1.7.6.4