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drm/amdgpu: zero-initialize GART table on allocation

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GART TLB is flushed after unmapping but not after mapping. Since
amdgpu_bo_create_kernel() does not zero-initialize the buffer, when a
single PTE is written the TLB may speculatively load other uninitialized
entries from the same cacheline. Those garbage entries can appear valid,
and a subsequent write to another PTE in the same cacheline may cause the
GPU to use a stale garbage PTE from the TLB.

Fix this by calling memset_io() to zero-initialize the GART table with
gart_pte_flags immediately after allocation.

Using AMDGPU_GEM_CREATE_VRAM_CLEARED, SDMA-based clear will not work
since SDMA needs GART to be initialized to work.

Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit d9af8263b82b6eaa60c5718e0c6631c5037e4b24)
Cc: stable@vger.kernel.org
This commit is contained in:
Philip Yang
2026-04-27 09:30:23 -04:00
committed by Alex Deucher
parent 78d2e624fa
commit e6c2e6c2e1
1 changed files with 10 additions and 3 deletions
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13
drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
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@@ -262,12 +262,19 @@ void amdgpu_gart_table_ram_free(struct amdgpu_device *adev)
*/
int amdgpu_gart_table_vram_alloc(struct amdgpu_device *adev)
{
int r;
if (adev->gart.bo != NULL)
return 0;
return amdgpu_bo_create_kernel(adev, adev->gart.table_size, PAGE_SIZE,
AMDGPU_GEM_DOMAIN_VRAM, &adev->gart.bo,
NULL, (void *)&adev->gart.ptr);
r = amdgpu_bo_create_kernel(adev, adev->gart.table_size, PAGE_SIZE,
AMDGPU_GEM_DOMAIN_VRAM, &adev->gart.bo,
NULL, (void *)&adev->gart.ptr);
if (r)
return r;
memset_io(adev->gart.ptr, adev->gart.gart_pte_flags, adev->gart.table_size);
return 0;
}
/**