drm/amdgpu: zero-initialize GART table on allocation

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>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
index bc772ca3dab726f136590b98cbcfdf0d75d7ff0a..b6f849d51c2e77a658fbf7b1e1d93502d26b45ac 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
@@ -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;
 }
 
 /**