On surprise removal the killed process's own exit path can fault on its SVM managed ranges: SIGBUS -> coredump -> get_dump_page() -> __get_user_pages() -> do_swap_page() -> svm_migrate_to_ram(). Without protection, svm_migrate_vram_to_ram() submits an SDMA copy job to an already-killed drm_sched entity (observed as "drm_sched_rq_add_entity: Trying to push to a killed entity" plus refcount_t saturation warnings), then svm_migrate_copy_done() waits uninterruptibly on a job fence that can never signal. The task dies in D state holding svms->lock, which wedges svm_range_restore_work() on the rwsem writer side, so kfd_processes_count never drains and the pciehp removal thread wedges for good.
Guard the hardware-accessing migration sections with drm_dev_enter()/drm_dev_exit() so unplug cannot proceed while a migration submits jobs and waits on them, and bound the job fence wait in svm_migrate_copy_done() with AMDGPU_FENCE_JIFFIES_TIMEOUT so a fence that can never signal does not stall the critical section (or the faulting task) indefinitely. Verified on MI50 behind Thunderbolt: the workload takes SIGBUS, coredump completes, kfd_processes_count drains in ~7s, pciehp removal finishes, and the device re-enumerates cleanly on slot re-power. Previously the same repro wedged the host. Cc: Xiaogang Chen <[email protected]> Signed-off-by: Olivier Kaloudoff <[email protected]> --- Changes in v5: - dropped drm_dev_is_unplugged()/pci_dev_is_disconnected() checks; drm_dev_enter()/exit() alone is sufficient (Felix Kuehling) Changes in v4: - use AMDGPU_FENCE_JIFFIES_TIMEOUT instead of an open-coded 10s (Felix Kuehling) - guard migration sections with drm_dev_enter()/exit() instead of racing flag checks (Felix Kuehling) - keep pci_dev_is_disconnected() early-out for the dead-link window - moved svm_range_restore_work() change to patch 2 Changes in v3: - new --- diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c index 253365a..14f2273 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c @@ -202,7 +202,17 @@ svm_migrate_copy_done(struct amdgpu_device *adev, struct dma_fence *mfence) int r = 0; if (mfence) { - r = dma_fence_wait(mfence, false); + /* Bound the wait: on a dying device the fence may never + * signal. + */ + long ret; + + ret = dma_fence_wait_timeout(mfence, false, + AMDGPU_FENCE_JIFFIES_TIMEOUT); + if (!ret) + r = -ETIMEDOUT; + else if (ret < 0) + r = ret; dma_fence_put(mfence); pr_debug("sdma copy memory fence done\n"); } @@ -494,6 +504,7 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc, u64 ttm_res_offset; struct kfd_node *node; unsigned long mpages = 0; + int idx; long r = 0; if (start_mgr < prange->start || last_mgr > prange->last) { @@ -507,6 +518,9 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc, pr_debug("failed to get kfd node by id 0x%x\n", best_loc); return -ENODEV; } + /* Block unplug while the migration submits jobs and waits on them */ + if (!drm_dev_enter(adev_to_drm(node->adev), &idx)) + return -ENODEV; pr_debug("svms 0x%p [0x%lx 0x%lx] in [0x%lx 0x%lx] to gpu 0x%x\n", prange->svms, start_mgr, last_mgr, prange->start, prange->last, @@ -521,6 +535,7 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc, node->xcp ? node->xcp->id : 0); if (r) { dev_dbg(node->adev->dev, "failed to reserve VRAM, r: %ld\n", r); + drm_dev_exit(idx); return -ENOSPC; } @@ -565,6 +580,7 @@ out: prange->npages * PAGE_SIZE, KFD_IOC_ALLOC_MEM_FLAGS_VRAM, node->xcp ? node->xcp->id : 0); + drm_dev_exit(idx); return r < 0 ? r : 0; } @@ -821,6 +837,7 @@ int svm_migrate_vram_to_ram(struct svm_range *prange, struct mm_struct *mm, unsigned long start; unsigned long end; unsigned long mpages = 0; + int idx; long r = 0; /* this pragne has no any vram page to migrate to sys ram */ @@ -841,6 +858,9 @@ int svm_migrate_vram_to_ram(struct svm_range *prange, struct mm_struct *mm, pr_debug("failed to get kfd node by id 0x%x\n", prange->actual_loc); return -ENODEV; } + /* Block unplug while the migration submits jobs and waits on them */ + if (!drm_dev_enter(adev_to_drm(node->adev), &idx)) + return -ENODEV; pr_debug("svms 0x%p prange 0x%p [0x%lx 0x%lx] from gpu 0x%x to ram\n", prange->svms, prange, start_mgr, last_mgr, prange->actual_loc); @@ -885,6 +905,7 @@ int svm_migrate_vram_to_ram(struct svm_range *prange, struct mm_struct *mm, } } + drm_dev_exit(idx); return r < 0 ? r : 0; } -- 2.47.3
