On 9/7/23 10:16, Boris Brezillon wrote:
On Wed, 6 Sep 2023 23:47:13 +0200
Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
@@ -812,15 +967,20 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
/**
* drm_gpuva_link() - link a &drm_gpuva
* @va: the &drm_gpuva to link
+ * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
*
- * This adds the given &va to the GPU VA list of the &drm_gem_object it is
- * associated with.
+ * This adds the given &va to the GPU VA list of the &drm_gpuvm_bo and the
+ * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
+ *
+ * For every &drm_gpuva entry added to the &drm_gpuvm_bo an additional
+ * reference of the latter is taken.
*
* This function expects the caller to protect the GEM's GPUVA list against
- * concurrent access using the GEMs dma_resv lock.
+ * concurrent access using either the GEMs dma_resv lock or a driver specific
+ * lock set through drm_gem_gpuva_set_lock().
*/
void
-drm_gpuva_link(struct drm_gpuva *va)
+drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
{
struct drm_gem_object *obj = va->gem.obj;
@@ -829,7 +989,10 @@ drm_gpuva_link(struct drm_gpuva *va)
drm_gem_gpuva_assert_lock_held(obj);
- list_add_tail(&va->gem.entry, &obj->gpuva.list);
+ drm_gpuvm_bo_get(vm_bo);
Guess we should WARN if vm_obj->obj == obj, at least.
+ list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
+ if (list_empty(&vm_bo->list.entry.gem))
+ list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
}
EXPORT_SYMBOL_GPL(drm_gpuva_link);
@@ -840,20 +1003,40 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
* This removes the given &va from the GPU VA list of the &drm_gem_object it is
* associated with.
*
+ * This removes the given &va from the GPU VA list of the &drm_gpuvm_bo and
+ * the &drm_gpuvm_bo from the &drm_gem_object it is associated with in case
+ * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
+ *
+ * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a reference of
+ * the latter is dropped.
+ *
* This function expects the caller to protect the GEM's GPUVA list against
- * concurrent access using the GEMs dma_resv lock.
+ * concurrent access using either the GEMs dma_resv lock or a driver specific
+ * lock set through drm_gem_gpuva_set_lock().
*/
void
drm_gpuva_unlink(struct drm_gpuva *va)
{
struct drm_gem_object *obj = va->gem.obj;
+ struct drm_gpuvm_bo *vm_bo;
if (unlikely(!obj))
return;
drm_gem_gpuva_assert_lock_held(obj);
+ vm_bo = __drm_gpuvm_bo_find(va->vm, obj);
Could we add a drm_gpuva::vm_bo field so we don't have to search the
vm_bo here, and maybe drop the drm_gpuva::vm and drm_gpuva::obj fields,
since drm_gpuvm_bo contains both the vm and the GEM object. I know that
means adding an extra indirection + allocation for drivers that don't
want to use drm_gpuva_[un]link(), but I wonder if it's not preferable
over having the information duplicated (with potential mismatch)
I was considering that and I think we can add a drm_gpuva::vm_bo field and
get rid of drm_gpuva::obj. However, I think we need to keep drm_gpuva::vm,
since it is valid for ::obj to be NULL, hence it must be valid for ::vm_bo too.
Null objects are used for sparse mappings / userptr.
+ if (WARN(!vm_bo, "GPUVA doesn't seem to be linked.\n"))
+ return;
+
list_del_init(&va->gem.entry);
+
+ /* This is the last mapping being unlinked for this GEM object, hence
+ * also remove the VM_BO from the GEM's gpuva list.
+ */
+ if (list_empty(&vm_bo->list.gpuva))
+ list_del_init(&vm_bo->list.entry.gem);
+ drm_gpuvm_bo_put(vm_bo);
}
EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
