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drm/amdgpu/ttm: Fix crash when handling MMIO_REMAP in PDE flags

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The MMIO_REMAP BO is a special 4K IO page that does not have a ttm_tt
behind it. However, amdgpu_ttm_tt_pde_flags() was treating it like
normal TT/doorbell/preempt memory and unconditionally accessed
ttm->caching. For the MMIO_REMAP BO, ttm is NULL, so this leads to a
NULL pointer dereference when computing PDE flags.

Fix this by checking that ttm is non-NULL before reading ttm->caching.
This prevents the crash for MMIO_REMAP and also makes the code more
defensive if other BOs ever come through without a ttm_tt.

Fixes: fb5a52dbe9 ("drm/amdgpu: Implement TTM handling for MMIO_REMAP placement")
Suggested-by: Jesse Zhang <Jesse.Zhang@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Jesse Zhang <Jesse.Zhang@amd.com>
Tested-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 0db94da5a0a1cacda080b9ec8425fcbe4babc141)
This commit is contained in:
Srinivasan Shanmugam
2025-11-18 14:28:33 +05:30
committed by Alex Deucher
parent a445923393
commit 21f46f5476
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
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@@ -1372,7 +1372,7 @@ uint64_t amdgpu_ttm_tt_pde_flags(struct ttm_tt *ttm, struct ttm_resource *mem)
mem->mem_type == AMDGPU_PL_MMIO_REMAP)) {
flags |= AMDGPU_PTE_SYSTEM;
if (ttm->caching == ttm_cached)
if (ttm && ttm->caching == ttm_cached)
flags |= AMDGPU_PTE_SNOOPED;
}