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

[Philip Yang]

On 2022-09-12 06:22, Christian König wrote:
Am 09.09.22 um 20:25 schrieb Philip Yang:
Free page table BO from vm resv unlocked context generate below
warnings.

Add a free_work in vm_bo base of each page table BO, pass vm resv
unlock status from page table update caller, 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.y...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h    |  3 ++
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 40 +++++++++++++++++++----
  2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 9ecb7f663e19..ac7cd2c738e5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -150,6 +150,9 @@ struct amdgpu_vm_bo_base {
        /* protected by the BO being reserved */
      bool                moved;
+
+    /* work to free pt bo if vm resv is not hold */
+    struct work_struct              free_work;

Oh, this is a pretty clear NAK. We can't increase the size of this 
struct.

Instead just come up with a single worker in the VM and a new state 
for the page tables.

Good idea, I agree it is too much overhead to add a worker in each pt 
bo. I will send v2 patch.

Regards,

Philip


Regards,
Christian.

  };
    /* provided by hw blocks that can write ptes, e.g., sdma */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
index 88de9f0d4728..e6f6d7e6368f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
@@ -37,6 +37,8 @@ struct amdgpu_vm_pt_cursor {
      unsigned int level;
  };
  +static void amdgpu_vm_pt_free_work(struct work_struct *work);
+
  /**
   * amdgpu_vm_pt_level_shift - return the addr shift for each level
   *
@@ -607,6 +609,7 @@ static int amdgpu_vm_pt_alloc(struct 
amdgpu_device *adev,
      pt_bo = &pt->bo;
      pt_bo->parent = amdgpu_bo_ref(cursor->parent->bo);
      amdgpu_vm_bo_base_init(entry, vm, pt_bo);
+    INIT_WORK(&entry->free_work, amdgpu_vm_pt_free_work);
      r = amdgpu_vm_pt_clear(adev, vm, pt, immediate);
      if (r)
          goto error_free_pt;
@@ -624,23 +627,46 @@ 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) {
+        schedule_work(&entry->free_work);
+        return;
+    }
+
      shadow = amdgpu_bo_shadowed(entry->bo);
      if (shadow) {
          ttm_bo_set_bulk_move(&shadow->tbo, NULL);
          amdgpu_bo_unref(&shadow);
      }
      ttm_bo_set_bulk_move(&entry->bo->tbo, NULL);
+
      entry->bo->vm_bo = NULL;
      list_del(&entry->vm_status);
      amdgpu_bo_unref(&entry->bo);
  }
  +static void amdgpu_vm_pt_free_work(struct work_struct *work)
+{
+    struct amdgpu_vm_bo_base *entry;
+    struct amdgpu_bo *root;
+
+    entry = container_of(work, struct amdgpu_vm_bo_base, delayed_work);
+
+    root = amdgpu_bo_ref(entry->vm->root.bo);
+    amdgpu_bo_reserve(root, true);
+
+    amdgpu_vm_pt_free(entry, true);
+
+    amdgpu_bo_unreserve(root);
+    amdgpu_bo_unref(&root);
+}
+
  /**
   * amdgpu_vm_pt_free_dfs - free PD/PT levels
   *
@@ -652,16 +678,17 @@ 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 +700,7 @@ 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 +993,8 @@ 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);
              }