kernel/linux.git/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c, branch v6.18.21

drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify

2026-03-04T12:21:29+00:00

[ Upstream commit b18fc0ab837381c1a6ef28386602cd888f2d9edf ] Invalidating a dmabuf will impact other users of the shared BO. In the scenario where process A moves the BO, it needs to inform process B about the move and process B will need to update its page table. The commit fixes a synchronisation bug caused by the use of the ticket: it made amdgpu_vm_handle_moved behave as if updating the page table immediately was correct but in this case it's not. An example is the following scenario, with 2 GPUs and glxgears running on GPU0 and Xorg running on GPU1, on a system where P2P PCI isn't supported: glxgears: export linear buffer from GPU0 and import using GPU1 submit frame rendering to GPU0 submit tiled->linear blit Xorg: copy of linear buffer The sequence of jobs would be: drm_sched_job_run # GPU0, frame rendering drm_sched_job_queue # GPU0, blit drm_sched_job_done # GPU0, frame rendering drm_sched_job_run # GPU0, blit move linear buffer for GPU1 access # amdgpu_dma_buf_move_notify -> update pt # GPU0 It this point the blit job on GPU0 is still running and would likely produce a page fault. Cc: stable@vger.kernel.org Fixes: a448cb003edc ("drm/amdgpu: implement amdgpu_gem_prime_move_notify v2") Signed-off-by: Pierre-Eric Pelloux-Prayer Reviewed-by: Christian König Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin

drm/amdgpu: disable peer-to-peer access for DCC-enabled GC12 VRAM surfaces

2025-11-12T03:49:19+00:00

Certain multi-GPU configurations (especially GFX12) may hit data corruption when a DCC-compressed VRAM surface is shared across GPUs using peer-to-peer (P2P) DMA transfers. Such surfaces rely on device-local metadata and cannot be safely accessed through a remote GPU’s page tables. Attempting to import a DCC-enabled surface through P2P leads to incorrect rendering or GPU faults. This change disables P2P for DCC-enabled VRAM buffers that are contiguous and allocated on GFX12+ hardware. In these cases, the importer falls back to the standard system-memory path, avoiding invalid access to compressed surfaces. Future work could consider optional migration (VRAM→System→VRAM) if a performance regression is observed when `attach->peer2peer = false`. Tested on: - Dual RX 9700 XT (Navi4x) setup - GNOME and Wayland compositor scenarios - Confirmed no corruption after disabling P2P under these conditions v2: Remove check TTM_PL_VRAM & TTM_PL_FLAG_CONTIGUOUS. v3: simplify for upsteam and fix ip version check (Alex) Suggested-by: Christian König Signed-off-by: Vitaly Prosyak Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit 9dff2bb709e6fbd97e263fd12bf12802d2b5a0cf) Cc: stable@vger.kernel.org

Merge tag 'v6.17-rc6' into drm-next

2025-09-15T07:51:07+00:00

This is a backmerge of Linux 6.17-rc6, needed for msm, also requested by misc. Signed-off-by: Dave Airlie

amdgpu: populate buffers before exporting them.

2025-09-11T00:04:31+00:00

Before exporting a buffer, make sure it has been populated with pages at least once. While discussing cgroups we noticed a problem where you could export a BO to a dma-buf without having it ever being backed or accounted for. This meant in low memory situations or eventually with cgroups, a lower privledged process might cause the compositor to try and allocate a lot of memory on it's behalf and this could fail. At least make sure the exporter has managed to allocate the RAM at least once before exporting the object. This only applies currently to TTM_PL_SYSTEM objects, because GTT objects get populated on first validate, and VRAM doesn't use TT. Reviewed-by: Christian Koenig Signed-off-by: Dave Airlie Link: https://lore.kernel.org/r/20250904021643.2050497-2-airlied@gmail.com

drm/amdgpu: Pin buffers while vmap'ing exported dma-buf objects

2025-08-22T12:05:31+00:00

Current dma-buf vmap semantics require that the mapped buffer remains in place until the corresponding vunmap has completed. For GEM-SHMEM, this used to be guaranteed by a pin operation while creating an S/G table in import. GEM-SHMEN can now import dma-buf objects without creating the S/G table, so the pin is missing. Leads to page-fault errors, such as the one shown below. [ 102.101726] BUG: unable to handle page fault for address: ffffc90127000000 [...] [ 102.157102] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl] [...] [ 102.243250] Call Trace: [ 102.245695] [ 102.2477V95] ? validate_chain+0x24e/0x5e0 [ 102.251805] ? __lock_acquire+0x568/0xae0 [ 102.255807] udl_render_hline+0x165/0x341 [udl] [ 102.260338] ? __pfx_udl_render_hline+0x10/0x10 [udl] [ 102.265379] ? local_clock_noinstr+0xb/0x100 [ 102.269642] ? __lock_release.isra.0+0x16c/0x2e0 [ 102.274246] ? mark_held_locks+0x40/0x70 [ 102.278177] udl_primary_plane_helper_atomic_update+0x43e/0x680 [udl] [ 102.284606] ? __pfx_udl_primary_plane_helper_atomic_update+0x10/0x10 [udl] [ 102.291551] ? lockdep_hardirqs_on_prepare.part.0+0x92/0x170 [ 102.297208] ? lockdep_hardirqs_on+0x88/0x130 [ 102.301554] ? _raw_spin_unlock_irq+0x24/0x50 [ 102.305901] ? wait_for_completion_timeout+0x2bb/0x3a0 [ 102.311028] ? drm_atomic_helper_calc_timestamping_constants+0x141/0x200 [ 102.317714] ? drm_atomic_helper_commit_planes+0x3b6/0x1030 [ 102.323279] drm_atomic_helper_commit_planes+0x3b6/0x1030 [ 102.328664] drm_atomic_helper_commit_tail+0x41/0xb0 [ 102.333622] commit_tail+0x204/0x330 [...] [ 102.529946] ---[ end trace 0000000000000000 ]--- [ 102.651980] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl] In this stack strace, udl (based on GEM-SHMEM) imported and vmap'ed a dma-buf from amdgpu. Amdgpu relocated the buffer, thereby invalidating the mapping. Provide a custom dma-buf vmap method in amdgpu that pins the object before mapping it's buffer's pages into kernel address space. Do the opposite in vunmap. Note that dma-buf vmap differs from GEM vmap in how it handles relocation. While dma-buf vmap keeps the buffer in place, GEM vmap requires the caller to keep the buffer in place. Hence, this fix is in amdgpu's dma-buf code instead of its GEM code. A discussion of various approaches to solving the problem is available at [1]. v3: - try (GTT | VRAM); drop CPU domain (Christian) v2: - only use mapable domains (Christian) - try pinning to domains in preferred order Signed-off-by: Thomas Zimmermann Fixes: 660cd44659a0 ("drm/shmem-helper: Import dmabuf without mapping its sg_table") Reported-by: Thomas Zimmermann Closes: https://lore.kernel.org/dri-devel/ba1bdfb8-dbf7-4372-bdcb-df7e0511c702@suse.de/ Cc: Shixiong Ou Cc: Thomas Zimmermann Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: David Airlie Cc: Simona Vetter Cc: Sumit Semwal Cc: "Christian König" Cc: dri-devel@lists.freedesktop.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Link: https://lore.kernel.org/dri-devel/9792c6c3-a2b8-4b2b-b5ba-fba19b153e21@suse.de/ # [1] Reviewed-by: Christian König Link: https://lore.kernel.org/r/20250821064031.39090-1-tzimmermann@suse.de

Revert "drm/amdgpu: Use dma_buf from GEM object instance"

2025-08-13T09:14:17+00:00

This reverts commit 515986100d176663d0a03219a3056e4252f729e6. The dma_buf field in struct drm_gem_object is not stable over the object instance's lifetime. The field becomes NULL when user space releases the final GEM handle on the buffer object. This resulted in a NULL-pointer deref. Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer: Acquire internal references on GEM handles") only solved the problem partially. They especially don't work for buffer objects without a DRM framebuffer associated. Hence, this revert to going back to using .import_attach->dmabuf. Signed-off-by: Thomas Zimmermann Reviewed-by: Simona Vetter Acked-by: Alex Deucher Link: https://lore.kernel.org/r/20250715082635.34974-1-tzimmermann@suse.de

drm/amdgpu: Use dma_buf from GEM object instance

2025-06-30T15:55:16+00:00

Avoid dereferencing struct drm_gem_object.import_attach for the imported dma-buf. The dma_buf field in the GEM object instance refers to the same buffer. Prepares to make import_attach an implementation detail of PRIME. Reviewed-by: Christian König Signed-off-by: Thomas Zimmermann Signed-off-by: Alex Deucher

drm/amdgpu: Test for imported buffers with drm_gem_is_imported()

2025-06-30T15:54:59+00:00

Instead of testing import_attach for imported GEM buffers, invoke drm_gem_is_imported() to do the test. v2: - keep amdgpu_bo_print_info() as-is (Christian) Reviewed-by: Christian König Signed-off-by: Thomas Zimmermann Signed-off-by: Alex Deucher

drm/amdgpu: Fail DMABUF map of XGMI-accessible memory

2025-05-01T15:01:46+00:00

If peer memory is XGMI-accessible, we should never access it through PCIe P2P DMA mappings. PCIe P2P is slower, has different coherence behaviour, limited or no support for atomics, or may not work at all. Fail with a warning if DMABUF mappings of such memory are attempted. Signed-off-by: Felix Kuehling Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit dbe4c63689bc6b5fd3ab72650ea4b6a667e96a68)

drm/amdgpu: Allow P2P access through XGMI

2025-04-22T20:47:12+00:00

If peer memory is accessible through XGMI, allow leaving it in VRAM rather than forcing its migration to GTT on DMABuf attachment. Signed-off-by: Felix Kuehling Tested-by: Hao (Claire) Zhou Reviewed-by: Christian König Signed-off-by: Alex Deucher (cherry picked from commit 372c8d72c3680fdea3fbb2d6b089f76b4a6d596a)