[Intel-xe] [PATCH] drm/xe: don't skip rebinds if there's a NULL binding involved

[Paulo Zanoni]

Commit a042bb4ca894 ("drm/xe: Avoid doing rebinds") causes
regressions in numerous Vulkan dEQP sparse-related tests. The errors
happen in tests that:

  - check residencyNonResidentStrict=true behavior (use NULL bindings
    and check that they read/write zero)
  - and use buffers bigger than 2MB
  - and write through sparse buffers using compute shaders with ssbos

So for example, the test:
  - dEQP-VK.sparse_resources.buffer.ssbo.sparse_residency.buffer_size_2_24

fails only if residencyNonResidentStrict is true, otherwise it passes
(becasue otherwise it doesn't check the values of the ranges that were
supposed to be bound through NULL bindings).

But the test:
  - dEQP-VK.sparse_resources.buffer.ssbo.sparse_residency.buffer_size_2_20

always passes because it uses a smaller buffer, despite doing
everything else equally. By maninpulating the sizes of the buffers we
can see that 2MB is the range where the test starts failing.

On the other hand, some other 2_24 tests were passing, despite having
4MB buffers and checking the contents of NULL binding buffers.

I can't claim I have a deep understanding of the code invovled here,
but this patch seems to be the minimal 'revert' that fixes the issue
and should be a good point to start the conversation on the mailing
list.

Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Testcase: dEQP-VK.sparse_resources.buffer.ssbo.sparse_residency.buffer_size_2_24
Fixes: a042bb4ca894 ("drm/xe: Avoid doing rebinds")
Reference: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23045
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 6429d6e5113d..955f664ff1f1 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -2512,7 +2512,8 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_engine *e,
 					 * Userptr creates a new SG mapping so
 					 * we must also rebind.
 					 */
-					op->remap.skip_prev = !xe_vma_is_userptr(old) &&
+					op->remap.skip_prev = !is_null &&
+						!xe_vma_is_userptr(old) &&
 						IS_ALIGNED(xe_vma_end(vma),
 							   xe_vma_max_pte_size(old));
 					if (op->remap.skip_prev) {
@@ -2547,7 +2548,8 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_engine *e,
 					 * Userptr creates a new SG mapping so
 					 * we must also rebind.
 					 */
-					op->remap.skip_next = !xe_vma_is_userptr(old) &&
+					op->remap.skip_next = !is_null &&
+						!xe_vma_is_userptr(old) &&
 						IS_ALIGNED(xe_vma_start(vma),
 							   xe_vma_max_pte_size(old));
 					if (op->remap.skip_next)
-- 
2.39.2