drm/virtio: use kvmalloc for large allocations

We observed that some of virtio_gpu_object_shmem_init() allocations
can be rather costly - order 6 - which can be difficult to fulfill
under memory pressure conditions. Switch to kvmalloc_array() in
virtio_gpu_object_shmem_init() and let the kernel vmalloc the entries
array.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20201105014744.1662226-1-senozhatsky@chromium.orgSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -184,7 +184,8 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
 		*nents = shmem->pages->orig_nents;
 	}
 
-	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
+	*ents = kvmalloc_array(*nents,
+			       sizeof(struct virtio_gpu_mem_entry),
 			       GFP_KERNEL);
 	if (!(*ents)) {
 		DRM_ERROR("failed to allocate ent list\n");