[PATCH 5.0 117/117] drm/virtio: do NOT reuse resource ids

Greg Kroah-Hartman
2019-04-15T19:14:48Z

From: Gerd Hoffmann <kraxel@redhat.com>

commit 16065fcdd19ddb9e093192914ac863884f308766 upstream.

Bisected guest kernel changes crashing qemu. Landed at
"6c1cd97bda drm/virtio: fix resource id handling". Looked again, and
noticed we where not only leaking *some* ids, but *all* ids. The old
code never ever called virtio_gpu_resource_id_put().

So, commit 6c1cd97bda effectively makes the linux kernel starting
re-using IDs after releasing them, and apparently virglrenderer can't
deal with that. Oops.

This patch puts a temporary stopgap into place for the 5.0 release.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208140409.15280-1-kraxel@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/virtio/virtgpu_object.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -28,10 +28,21 @@
static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
uint32_t *resid)
{
+#if 0
int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);

if (handle < 0)
return handle;
+#else
+ static int handle;
+
+ /*
+ * FIXME: dirty hack to avoid re-using IDs, virglrenderer
+ * can't deal with that. Needs fixing in virglrenderer, also
+ * should figure a better way to handle that in the guest.
+ */
+ handle++;
+#endif

*resid = handle + 1;
return 0;
@@ -39,7 +50,9 @@ static int virtio_gpu_resource_id_get(st

static void virtio_gpu_resource_id_put(struct virtio_gpu_device *vgdev, uint32_t id)
{
+#if 0
ida_free(&vgdev->resource_ida, id - 1);
+#endif
}

static void virtio_gpu_ttm_bo_destroy(struct ttm_buffer_object *tbo)