drm/xe: Convert remaining instances of ttm_eu_reserve_buffers to drm_exec

The VM_BIND functionality and vma destruction was locking
potentially multiple dma_resv objects using the
ttm_eu_reserve_buffers() function. Rework those to use the drm_exec
helper, taking care that any calls to xe_bo_validate() ends up
inside an unsealed locking transaction.

v4:
- Remove an unbalanced xe_bo_put() (igt and Matthew Brost)
v5:
- Rebase conflict
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230908091716.36984-7-thomas.hellstrom@linux.intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_vm.c

@@ -1129,29 +1129,20 @@ int xe_vm_prepare_vma(struct drm_exec *exec, struct xe_vma *vma,
 
 static void xe_vma_destroy_unlocked(struct xe_vma *vma)
 {
-	struct ttm_validate_buffer tv[2];
-	struct ww_acquire_ctx ww;
-	struct xe_bo *bo = xe_vma_bo(vma);
-	LIST_HEAD(objs);
-	LIST_HEAD(dups);
+	struct drm_exec exec;
 	int err;
 
-	memset(tv, 0, sizeof(tv));
-	tv[0].bo = xe_vm_ttm_bo(xe_vma_vm(vma));
-	list_add(&tv[0].head, &objs);
-
-	if (bo) {
-		tv[1].bo = &xe_bo_get(bo)->ttm;
-		list_add(&tv[1].head, &objs);
+	drm_exec_init(&exec, 0);
+	drm_exec_until_all_locked(&exec) {
+		err = xe_vm_prepare_vma(&exec, vma, 0);
+		drm_exec_retry_on_contention(&exec);
+		if (XE_WARN_ON(err))
+			break;
 	}
-	err = ttm_eu_reserve_buffers(&ww, &objs, false, &dups);
-	XE_WARN_ON(err);
 
 	xe_vma_destroy(vma, NULL);
 
-	ttm_eu_backoff_reservation(&ww, &objs);
-	if (bo)
-		xe_bo_put(bo);
+	drm_exec_fini(&exec);
 }
 
 struct xe_vma *
@@ -2142,21 +2133,6 @@ static int xe_vm_prefetch(struct xe_vm *vm, struct xe_vma *vma,
 
 #define VM_BIND_OP(op)	(op & 0xffff)
 
-struct ttm_buffer_object *xe_vm_ttm_bo(struct xe_vm *vm)
-{
-	int idx = vm->flags & XE_VM_FLAG_MIGRATION ?
-		XE_VM_FLAG_TILE_ID(vm->flags) : 0;
-
-	/* Safe to use index 0 as all BO in the VM share a single dma-resv lock */
-	return &vm->pt_root[idx]->bo->ttm;
-}
-
-static void xe_vm_tv_populate(struct xe_vm *vm, struct ttm_validate_buffer *tv)
-{
-	tv->num_shared = 1;
-	tv->bo = xe_vm_ttm_bo(vm);
-}
-
 static void vm_set_async_error(struct xe_vm *vm, int err)
 {
 	lockdep_assert_held(&vm->lock);
@@ -2668,42 +2644,16 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
 	return err;
 }
 
-static int __xe_vma_op_execute(struct xe_vm *vm, struct xe_vma *vma,
-			       struct xe_vma_op *op)
+static int op_execute(struct drm_exec *exec, struct xe_vm *vm,
+		      struct xe_vma *vma, struct xe_vma_op *op)
 {
-	LIST_HEAD(objs);
-	LIST_HEAD(dups);
-	struct ttm_validate_buffer tv_bo, tv_vm;
-	struct ww_acquire_ctx ww;
-	struct xe_bo *vbo;
 	int err;
 
 	lockdep_assert_held_write(&vm->lock);
 
-	xe_vm_tv_populate(vm, &tv_vm);
-	list_add_tail(&tv_vm.head, &objs);
-	vbo = xe_vma_bo(vma);
-	if (vbo) {
-		/*
-		 * An unbind can drop the last reference to the BO and
-		 * the BO is needed for ttm_eu_backoff_reservation so
-		 * take a reference here.
-		 */
-		xe_bo_get(vbo);
-
-		if (!vbo->vm) {
-			tv_bo.bo = &vbo->ttm;
-			tv_bo.num_shared = 1;
-			list_add(&tv_bo.head, &objs);
-		}
-	}
-
-again:
-	err = ttm_eu_reserve_buffers(&ww, &objs, true, &dups);
-	if (err) {
-		xe_bo_put(vbo);
+	err = xe_vm_prepare_vma(exec, vma, 1);
+	if (err)
 		return err;
-	}
 
 	xe_vm_assert_held(vm);
 	xe_bo_assert_held(xe_vma_bo(vma));
@@ -2782,17 +2732,36 @@ static int __xe_vma_op_execute(struct xe_vm *vm, struct xe_vma *vma,
 		XE_WARN_ON("NOT POSSIBLE");
 	}
 
-	ttm_eu_backoff_reservation(&ww, &objs);
+	if (err)
+		trace_xe_vma_fail(vma);
+
+	return err;
+}
+
+static int __xe_vma_op_execute(struct xe_vm *vm, struct xe_vma *vma,
+			       struct xe_vma_op *op)
+{
+	struct drm_exec exec;
+	int err;
+
+retry_userptr:
+	drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
+	drm_exec_until_all_locked(&exec) {
+		err = op_execute(&exec, vm, vma, op);
+		drm_exec_retry_on_contention(&exec);
+		if (err)
+			break;
+	}
+	drm_exec_fini(&exec);
+
 	if (err == -EAGAIN && xe_vma_is_userptr(vma)) {
 		lockdep_assert_held_write(&vm->lock);
 		err = xe_vma_userptr_pin_pages(vma);
 		if (!err)
-			goto again;
-	}
-	xe_bo_put(vbo);
+			goto retry_userptr;
 
-	if (err)
 		trace_xe_vma_fail(vma);
+	}
 
 	return err;
 }

drivers/gpu/drm/xe/xe_vm.h

@@ -180,8 +180,6 @@ int xe_vm_async_fence_wait_start(struct dma_fence *fence);
 
 extern struct ttm_device_funcs xe_ttm_funcs;
 
-struct ttm_buffer_object *xe_vm_ttm_bo(struct xe_vm *vm);
-
 static inline void xe_vm_queue_rebind_worker(struct xe_vm *vm)
 {
 	XE_WARN_ON(!xe_vm_in_compute_mode(vm));