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Running RCCL unit tests on a system with a 64K PAGE_SIZE triggers the following warning and causes the test to terminate on latest upstream kernel: WARNING: drivers/gpu/drm/amd/amdgpu/amdgpu_object.c:1335 at amdgpu_bo_release_notify+0x1bc/0x280 [amdgpu], CPU#18: rccl-UnitTests/33151 Call trace: amdgpu_bo_release_notify ttm_bo_release amdgpu_gem_object_free drm_gem_object_free amdgpu_bo_unref amdgpu_bo_create amdgpu_bo_create_user amdgpu_gem_object_create amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu kfd_ioctl_alloc_memory_of_gpu kfd_ioctl sys_ioctl The warning is triggered because amdgpu_ttm_next_clear_entity() returns NULL when a clear buffer operation is requested. This happens because the GART window allocation for the default_entity, clear_entity and move_entity fails during initialization. Commit [1] introduced separate GART windows for the default_entity, clear_entity and move_entity of each SDMA instance. Their sizes are derived from AMDGPU_GTT_MAX_TRANSFER_SIZE, which is currently defined as 1024 pages. This implicitly assumes a 4K PAGE_SIZE, where 1024 pages correspond to a 4MB transfer. On a 64K PAGE_SIZE system, however, the same value expands to 64MB. The default_entity and clear_entity each allocate one AMDGPU_GTT_MAX_TRANSFER_SIZE GART window, while the move_entity allocates two such windows. This results in 16MB of GART space per SDMA instance on a 4K PAGE_SIZE system, but 256MB per SDMA instance on a 64K PAGE_SIZE system. On an MI210 system with five SDMA instances and a 512MB GART aperture, the total GART space required becomes 1.25GB, exceeding the available GART aperture. Consequently, GART window allocation fails, amdgpu_ttm_next_clear_entity() returns NULL, and the above warning is triggered. Redefine AMDGPU_GTT_MAX_TRANSFER_SIZE in bytes instead of page units. Where a page count is required, convert it using PAGE_SHIFT. This preserves the existing 4MB transfer size across all PAGE_SIZE configurations while keeping GART window allocations within the available GART aperture. [1] https://lore.kernel.org/all/20260408100327.1372-3-pierre-eric.pelloux-prayer@amd.com/#t Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5435 Fixes:897ee11ec0("drm/amdgpu: create multiple clear/move ttm entities") Signed-off-by: Donet Tom <donettom@linux.ibm.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> (cherry picked from commit27213b776a) Cc: stable@vger.kernel.org