Re: [PATCH v1 0/2] virtio: fix for assertion failure: virtio_net_get_subqueue(nc)->async_tx.elem failed

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jan 29, 2023 at 10:51:48AM +0800, Xuan Zhuo wrote:
> In the current design, we stop the device from operating on the vring
> during per-queue reset by resetting the structure VirtQueue.
> 
> But before the reset operation, when recycling some resources, we should
> stop referencing new vring resources.
> 
> This bug is caused by this reason.
> 
>     https://gitlab.com/qemu-project/qemu/-/issues/1451
> 
> Before we reset the structure, we called the ->queue_reset callback to let the
> device reclaim resources. Here virtio-net tries to release the packets sent
> asynchronously, but during this process virtio_net_flush_tx() will be called,
> and new data will be sent again. This leads to asserted.
> 
>      assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
> 
> This patch set introduce new item "reset" into struct VirtQueue, then device can
> know this virtqueue is per-queue reset state.

Better but I still don't exacctly understand what this state means.
Sent some questions on the patches themselves.
Thanks!


> v1:
>     1. rename "reset" to disabled_by_reset
>     2. add api: virtio_queue_reset_state()
> 
> Xuan Zhuo (2):
>   virtio: struct VirtQueue introduce reset
>   virtio-net: virtio_net_flush_tx() check for per-queue reset
> 
>  hw/net/virtio-net.c        |  3 ++-
>  hw/virtio/virtio.c         | 15 +++++++++++++++
>  include/hw/virtio/virtio.h |  1 +
>  3 files changed, 18 insertions(+), 1 deletion(-)
> 
> --
> 2.32.0.3.g01195cf9f