From: Junrui Luo <[email protected]>
amdgpu_cs_patch_ibs() derives the CPU-side view of a UVD/VCE/VCN
indirect buffer from the BO returned by amdgpu_cs_find_mapping():
r = amdgpu_bo_kmap(aobj, (void **)&kptr);
kptr += va_start - (m->start * AMDGPU_GPU_PAGE_SIZE);
amdgpu_bo_kmap() returns the start of the BO, so only the displacement
of va_start inside the mapping is added. The page tables, however, are
programmed from mapping->offset (see amdgpu_vm_bo_update()), which
records the offset_in_bo the client passed to AMDGPU_GEM_VA. The GPU
therefore resolves va_start to BO byte
m->offset + (va_start - m->start * AMDGPU_GPU_PAGE_SIZE)
while the kernel inspects the byte m->offset lower. Whenever an IB is
submitted through a mapping created with a non-zero offset_in_bo, the
two views disagree.
Add the missing term so the kmapped pointer describes the same bytes the
page tables do.
Every other CPU-side consumer of amdgpu_cs_find_mapping() omits
mapping->offset in the same way.
Reported-by: Yuhao Jiang <[email protected]>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Junrui Luo <[email protected]>
Reviewed-by: Christian König <[email protected]>
---
Changes in v2:
- Drop the Fixes tag.
- Pick up Christian's Reviewed-by.
- Resend standalone.
- Link to v1:
https://lore.kernel.org/r/[email protected]
---
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 5445f75741b5..17fe6d56e020 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1043,7 +1043,7 @@ static int amdgpu_cs_patch_ibs(struct amdgpu_cs_parser *p,
if (r)
return r;
- kptr += va_start - (m->start * AMDGPU_GPU_PAGE_SIZE);
+ kptr += m->offset + va_start - (m->start *
AMDGPU_GPU_PAGE_SIZE);
if (ring->funcs->parse_cs) {
memcpy(ib->ptr, kptr, ib->length_dw * 4);
---
base-commit: 075b74841bd0065a3bda3440873c747938e69b68
change-id: 20260808-amdgpu-fixes-9ca10fa07e10
Best regards,
--
Junrui Luo <[email protected]>
