drm/xe: Skip VMAs pin when requesting signal to the last XE_EXEC

Doing a XE_EXEC with num_batch_buffer == 0 makes signals passed as
argument to be signaled when the last real XE_EXEC is completed.
But to do that it was first pinning all VMAs in drm_gpuvm_exec_lock(),
this patch remove this pinning as it is not required.

This change also help Mesa implementing memory over-commiting recovery
as it needs to unbind not needed VMAs when the whole VM can't fit
in GPU memory but it can only do the unbiding when the last XE_EXEC
is completed.
So with this change Mesa can get the signal it want without getting
out-of-memory errors.

Fixes: eb9702ad ("drm/xe: Allow num_batch_buffer / num_binds == 0 in IOCTLs")
Cc: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Co-developed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240313171318.121066-1-jose.souza@intel.com

drivers/gpu/drm/xe/xe_exec.c

@@ -235,6 +235,29 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 			goto err_unlock_list;
 	}
 
+	if (!args->num_batch_buffer) {
+		err = xe_vm_lock(vm, true);
+		if (err)
+			goto err_unlock_list;
+
+		if (!xe_vm_in_lr_mode(vm)) {
+			struct dma_fence *fence;
+
+			fence = xe_sync_in_fence_get(syncs, num_syncs, q, vm);
+			if (IS_ERR(fence)) {
+				err = PTR_ERR(fence);
+				goto err_unlock_list;
+			}
+			for (i = 0; i < num_syncs; i++)
+				xe_sync_entry_signal(&syncs[i], NULL, fence);
+			xe_exec_queue_last_fence_set(q, vm, fence);
+			dma_fence_put(fence);
+		}
+
+		xe_vm_unlock(vm);
+		goto err_unlock_list;
+	}
+
 	vm_exec.vm = &vm->gpuvm;
 	vm_exec.flags = DRM_EXEC_INTERRUPTIBLE_WAIT;
 	if (xe_vm_in_lr_mode(vm)) {
@@ -254,24 +277,6 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 		goto err_exec;
 	}
 
-	if (!args->num_batch_buffer) {
-		if (!xe_vm_in_lr_mode(vm)) {
-			struct dma_fence *fence;
-
-			fence = xe_sync_in_fence_get(syncs, num_syncs, q, vm);
-			if (IS_ERR(fence)) {
-				err = PTR_ERR(fence);
-				goto err_exec;
-			}
-			for (i = 0; i < num_syncs; i++)
-				xe_sync_entry_signal(&syncs[i], NULL, fence);
-			xe_exec_queue_last_fence_set(q, vm, fence);
-			dma_fence_put(fence);
-		}
-
-		goto err_exec;
-	}
-
 	if (xe_exec_queue_is_lr(q) && xe_exec_queue_ring_full(q)) {
 		err = -EWOULDBLOCK;	/* Aliased to -EAGAIN */
 		skip_retry = true;