Commit 23c18c71 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

drm/i915: fixup in-line clflushing on bit17 swizzled bos



The issue is that with inline clflushing the clflushing isn't properly
swizzled. Fix this by
- always clflushing entire 128 byte chunks and
- unconditionally flush before writes when swizzling a given page.
  We could be clever and check whether we pwrite a partial 128 byte
  chunk instead of a partial cacheline, but I've figured that's not
  worth it.

Now the usual approach is to fold this into the original patch series, but
I've opted against this because
- this fixes a corner case only very old userspace relies on and
- I'd like to not invalidate all the testing the pwrite rewrite has gotten.

This fixes the regression notice by tests/gem_tiled_partial_prite_pread
from i-g-t. Unfortunately it doesn't fix the issues with partial pwrites to
tiled buffers on bit17 swizzling machines. But that is also broken without
the pwrite patches, so likely a different issue (or a problem with the
testcase).

v2: Simplify the patch by dropping the overly clever partial write
logic for swizzled pages.

Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent f56f821f
......@@ -313,6 +313,28 @@ shmem_pread_fast(struct page *page, int shmem_page_offset, int page_length,
return ret;
}
static void
shmem_clflush_swizzled_range(char *addr, unsigned long length,
bool swizzled)
{
if (swizzled) {
unsigned long start = (unsigned long) addr;
unsigned long end = (unsigned long) addr + length;
/* For swizzling simply ensure that we always flush both
* channels. Lame, but simple and it works. Swizzled
* pwrite/pread is far from a hotpath - current userspace
* doesn't use it at all. */
start = round_down(start, 128);
end = round_up(end, 128);
drm_clflush_virt_range((void *)start, end - start);
} else {
drm_clflush_virt_range(addr, length);
}
}
/* Only difference to the fast-path function is that this can handle bit17
* and uses non-atomic copy and kmap functions. */
static int
......@@ -325,8 +347,9 @@ shmem_pread_slow(struct page *page, int shmem_page_offset, int page_length,
vaddr = kmap(page);
if (needs_clflush)
drm_clflush_virt_range(vaddr + shmem_page_offset,
page_length);
shmem_clflush_swizzled_range(vaddr + shmem_page_offset,
page_length,
page_do_bit17_swizzling);
if (page_do_bit17_swizzling)
ret = __copy_to_user_swizzled(user_data,
......@@ -637,9 +660,10 @@ shmem_pwrite_slow(struct page *page, int shmem_page_offset, int page_length,
int ret;
vaddr = kmap(page);
if (needs_clflush_before)
drm_clflush_virt_range(vaddr + shmem_page_offset,
page_length);
if (needs_clflush_before || page_do_bit17_swizzling)
shmem_clflush_swizzled_range(vaddr + shmem_page_offset,
page_length,
page_do_bit17_swizzling);
if (page_do_bit17_swizzling)
ret = __copy_from_user_swizzled(vaddr, shmem_page_offset,
user_data,
......@@ -649,8 +673,9 @@ shmem_pwrite_slow(struct page *page, int shmem_page_offset, int page_length,
user_data,
page_length);
if (needs_clflush_after)
drm_clflush_virt_range(vaddr + shmem_page_offset,
page_length);
shmem_clflush_swizzled_range(vaddr + shmem_page_offset,
page_length,
page_do_bit17_swizzling);
kunmap(page);
return ret;
......
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