Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] Iterating over `p->exec` objects for validation inadvertently validates victim BOs that were just evicted, breaking VRAM overcommit. - [Medium] Buffer migration budget is bypassed when a submission retries due to lock contention. --
commit 106f3922010dddea6e74f4d9b1260b3b5ba91adf Author: Christian König <[email protected]> drm/amdgpu: use drm_exec during BO validation This commit modifies the CS parser BO validation sequence to use the drm_exec infrastructure, aiming to detect and handle deadlocks caused by resource constraints during eviction. > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c > index c2e6495a28bc5..052d41013f7a0 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c [ ... ] > @@ -922,47 +923,53 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser > *p, > if (unlikely(r)) > goto out_free_user_pages; > } [ ... ] > - amdgpu_cs_get_threshold_for_moves(p->adev, &p->bytes_moved_threshold, > - &p->bytes_moved_vis_threshold); > - p->bytes_moved = 0; > - p->bytes_moved_vis = 0; > - > - r = amdgpu_vm_validate(p->adev, &fpriv->vm, NULL, > - amdgpu_cs_bo_validate, p); > - if (r) { > - drm_err(adev_to_drm(p->adev), "amdgpu_vm_validate() failed.\n"); > - goto out_free_user_pages; > - } > + amdgpu_cs_get_threshold_for_moves(p->adev, > &p->bytes_moved_threshold, > + > &p->bytes_moved_vis_threshold); > + p->bytes_moved = 0; > + p->bytes_moved_vis = 0; [Severity: Medium] If a submission physically moves buffers but then hits lock contention later in the execution, drm_exec_retry_on_contention() will restart the drm_exec_until_all_locked() loop. Does resetting p->bytes_moved and p->bytes_moved_vis to 0 here cause the driver to lose track of the bytes already moved during the aborted pass? When the retry finally succeeds, it appears amdgpu_cs_report_moved_bytes() will only report the final pass, which might bypass the migration budget throttling logic and leak the physical migration costs already incurred. > + r = amdgpu_vm_validate(p->adev, &fpriv->vm, NULL, > + amdgpu_cs_bo_validate, p); > + drm_exec_retry_on_contention(&p->exec); > + if (r) { > + drm_err(adev_to_drm(p->adev), "amdgpu_vm_validate() > failed.\n"); > goto out_free_user_pages; > + } > + > + drm_exec_for_each_locked_object(&p->exec, obj) { > + r = amdgpu_cs_bo_validate(p, gem_to_amdgpu_bo(obj)); [Severity: High] When TTM evicts a buffer, does it use ctx.exec (which now points to p->exec after this patch) to lock the victim BO? If so, it seems the victim BO gets added to the p->exec locked objects list. Since this drm_exec_for_each_locked_object() loop blindly iterates over all objects in p->exec, won't it inadvertently validate the newly evicted victim BO as well? Calling amdgpu_cs_bo_validate() on the victim could attempt to move it back to its preferred domain in VRAM, which seems like it would defeat the eviction entirely and potentially break VRAM overcommit. > + drm_exec_retry_on_contention(&p->exec); > + if (unlikely(r)) > + goto out_free_user_pages; > + } > + > + amdgpu_cs_report_moved_bytes(p->adev, p->bytes_moved, > + p->bytes_moved_vis); > } -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=10
