Re: [PATCH v2 1/1] drm/amdgpu: fix amdgpu_vm_pt_free warning

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Am 12.09.22 um 20:48 schrieb Felix Kuehling:
Am 2022-09-12 um 13:58 schrieb Philip Yang:
Free page table BO from vm resv unlocked context generate below
warnings.

Add a free_bo_work in vm to free page able BO from vm->bo_freed list.
pass vm resv unlock status from page table update caller, and add vm_bo
entry to vm->bo_freed_list and schedule the work if calling with vm resv
unlocked.

WARNING: CPU: 12 PID: 3238 at
drivers/gpu/drm/ttm/ttm_bo.c:106 ttm_bo_set_bulk_move+0xa1/0xc0
Call Trace:
  amdgpu_vm_pt_free+0x42/0xd0 [amdgpu]
  amdgpu_vm_pt_free_dfs+0xb3/0xf0 [amdgpu]
  amdgpu_vm_ptes_update+0x52d/0x850 [amdgpu]
  amdgpu_vm_update_range+0x2a6/0x640 [amdgpu]
  svm_range_unmap_from_gpus+0x110/0x300 [amdgpu]
  svm_range_cpu_invalidate_pagetables+0x535/0x600 [amdgpu]
  __mmu_notifier_invalidate_range_start+0x1cd/0x230
  unmap_vmas+0x9d/0x140
  unmap_region+0xa8/0x110

WARNING: CPU: 0 PID: 1475 at
drivers/dma-buf/dma-resv.c:483 dma_resv_iter_next
Call Trace:
  dma_resv_iter_first+0x43/0xa0
  amdgpu_vm_sdma_update+0x69/0x2d0 [amdgpu]
  amdgpu_vm_ptes_update+0x29c/0x870 [amdgpu]
  amdgpu_vm_update_range+0x2f6/0x6c0 [amdgpu]
  svm_range_unmap_from_gpus+0x115/0x300 [amdgpu]
  svm_range_cpu_invalidate_pagetables+0x510/0x5e0 [amdgpu]
  __mmu_notifier_invalidate_range_start+0x1d3/0x230
  unmap_vmas+0x140/0x150
  unmap_region+0xa8/0x110

Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c    |  4 ++
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h    |  6 +++
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 51 ++++++++++++++++++++---
  3 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 59cac347baa3..add3b08ffde9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2022,6 +2022,9 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm)
      spin_lock_init(&vm->invalidated_lock);
      INIT_LIST_HEAD(&vm->freed);
      INIT_LIST_HEAD(&vm->done);
+    INIT_LIST_HEAD(&vm->bo_freed);
+    INIT_WORK(&vm->bo_free_work, amdgpu_vm_pt_free_work);
+    spin_lock_init(&vm->bo_free_lock);
        /* create scheduler entities for page table updates */
      r = drm_sched_entity_init(&vm->immediate, DRM_SCHED_PRIORITY_NORMAL, @@ -2244,6 +2247,7 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
          amdgpu_vm_free_mapping(adev, vm, mapping, NULL);
      }
  +    cancel_work_sync(&vm->bo_free_work);
      amdgpu_vm_pt_free_root(adev, vm);
      amdgpu_bo_unreserve(root);
      amdgpu_bo_unref(&root);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 9ecb7f663e19..c8c59c66ca2f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -276,6 +276,11 @@ struct amdgpu_vm {
      /* BOs which are invalidated, has been updated in the PTs */
      struct list_head        done;
  +    /* PT BOs scheduled to free and fill with zero if vm_resv is not hold */
+    struct list_head    bo_freed;
+    struct work_struct    bo_free_work;
+    spinlock_t        bo_free_lock;
+
      /* contains the page directory */
      struct amdgpu_vm_bo_base     root;
      struct dma_fence    *last_update;
@@ -471,6 +476,7 @@ int amdgpu_vm_pde_update(struct amdgpu_vm_update_params *params,
  int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
                uint64_t start, uint64_t end,
                uint64_t dst, uint64_t flags);
+void amdgpu_vm_pt_free_work(struct work_struct *work);
    #if defined(CONFIG_DEBUG_FS)
  void amdgpu_debugfs_vm_bo_info(struct amdgpu_vm *vm, struct seq_file *m); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
index 88de9f0d4728..12471ef126a9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
@@ -624,12 +624,22 @@ static int amdgpu_vm_pt_alloc(struct amdgpu_device *adev,
   *
   * @entry: PDE to free
   */
-static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
+static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry, bool unlocked)
  {
      struct amdgpu_bo *shadow;
        if (!entry->bo)
          return;
+
+    if (unlocked) {
+        spin_lock(&entry->vm->bo_free_lock);
+        list_move(&entry->vm_status, &entry->vm->bo_freed);
+        spin_unlock(&entry->vm->bo_free_lock);
+
+        schedule_work(&entry->vm->bo_free_work);
+        return;
+    }
+
      shadow = amdgpu_bo_shadowed(entry->bo);
      if (shadow) {
          ttm_bo_set_bulk_move(&shadow->tbo, NULL);
@@ -641,6 +651,33 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
      amdgpu_bo_unref(&entry->bo);
  }
  +void amdgpu_vm_pt_free_work(struct work_struct *work)
+{
+    struct amdgpu_vm_bo_base *entry;
+    struct amdgpu_vm *vm;
+    struct amdgpu_bo *root;
+
+    vm = container_of(work, struct amdgpu_vm, bo_free_work);
+
+    root = amdgpu_bo_ref(vm->root.bo);
+    amdgpu_bo_reserve(root, true);
+
+    spin_lock(&vm->bo_free_lock);
+    while (!list_empty(&vm->bo_freed)) {
+        entry = list_first_entry(&vm->bo_freed, struct amdgpu_vm_bo_base,
+                     vm_status);

I don't see where you're removing the entry from the list. You need a list_del_init here.

If you're relying on the list_del call in amdgpu_vm_pt_free, that's not safe because it's outside the spinlock. This could end up corrupting the list if another thread is concurrently adding to the same list.

It's much easier to use list_splice() to move the list to a local head and then traverse it with list_for_each_entry_safe() and free up everything.

Regards,
Christian.


Regards,
  Felix


+ spin_unlock(&vm->bo_free_lock);
+
+        amdgpu_vm_pt_free(entry, false);
+
+        spin_lock(&vm->bo_free_lock);
+    }
+    spin_unlock(&vm->bo_free_lock);
+
+    amdgpu_bo_unreserve(root);
+    amdgpu_bo_unref(&root);
+}
+
  /**
   * amdgpu_vm_pt_free_dfs - free PD/PT levels
   *
@@ -652,16 +689,17 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
   */
  static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
                    struct amdgpu_vm *vm,
-                  struct amdgpu_vm_pt_cursor *start)
+                  struct amdgpu_vm_pt_cursor *start,
+                  bool unlocked)
  {
      struct amdgpu_vm_pt_cursor cursor;
      struct amdgpu_vm_bo_base *entry;
        for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
-        amdgpu_vm_pt_free(entry);
+        amdgpu_vm_pt_free(entry, unlocked);
        if (start)
-        amdgpu_vm_pt_free(start->entry);
+        amdgpu_vm_pt_free(start->entry, unlocked);
  }
    /**
@@ -673,7 +711,7 @@ static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
   */
  void amdgpu_vm_pt_free_root(struct amdgpu_device *adev, struct amdgpu_vm *vm)
  {
-    amdgpu_vm_pt_free_dfs(adev, vm, NULL);
+    amdgpu_vm_pt_free_dfs(adev, vm, NULL, false);
  }
    /**
@@ -966,7 +1004,8 @@ int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
                  if (cursor.entry->bo) {
                      params->table_freed = true;
                      amdgpu_vm_pt_free_dfs(adev, params->vm,
-                                  &cursor);
+                                  &cursor,
+                                  params->unlocked);
                  }
                  amdgpu_vm_pt_next(adev, &cursor);
              }




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