Re: [PATCH v7 10/10] virtio-net: add peer_deleted check in virtio_net_handle_rx

[Jason Wang]

在 2021/6/2 上午11:47, Cindy Lu 写道:
> During the test, We found this function will continue running
> while the peer is deleted, this will cause the crash. so add
> check for this. this only exist in  machines type microvm


Any idea why it only happens on microvm?


> reproduce step :
> load the VM with
> qemu-system-x86_64 -M microvm
> ...
>      -netdev tap,id=tap0,vhost=on,script=no,downscript=no \
>      -device virtio-net-device,netdev=tap0 \
> ..
> enter the VM's console
> shutdown the VM
> (gdb) bt
>
> 0  0x000055555595b926 in qemu_net_queue_flush (queue=0x0) at ../net/queue.c:275


So which piece of code trigger this? When the nc has a NIC peer we don't 
free it until the NIC is freed.


> 1  0x0000555555a046ea in qemu_flush_or_purge_queued_packets (nc=0x555556ccb920, 
> purge=false)
>      at ../net/net.c:624
> 2  0x0000555555a04736 in qemu_flush_queued_packets (nc=0x555556ccb920) at 
> ../net/net.c:637
> 3  0x0000555555ccc01a in virtio_net_handle_rx (vdev=0x555557360ed0, 
> vq=0x7ffff40d6010)
>      at ../hw/net/virtio-net.c:1401
> 4  0x0000555555ce907a in virtio_queue_notify_vq (vq=0x7ffff40d6010) at 
> ../hw/virtio/virtio.c:2346
> 5  0x0000555555cec07c in virtio_queue_host_notifier_read (n=0x7ffff40d608c)
>      at ../hw/virtio/virtio.c:3606
> 6  0x00005555560376ac in aio_dispatch_handler (ctx=0x555556a857e0, 
> node=0x555556f013d0)
>      at ../util/aio-posix.c:329
> 7  0x00005555560377a4 in aio_dispatch_ready_handlers (ctx=0x555556a857e0,
>      ready_list=0x7fffffffdfe0) at ../util/aio-posix.c:359
> 8  0x0000555556038209 in aio_poll (ctx=0x555556a857e0, blocking=false) at 
> ../util/aio-posix.c:662
> 9  0x0000555555e51c6f in monitor_cleanup () at ../monitor/monitor.c:637
> 10 0x0000555555d2d626 in qemu_cleanup () at ../softmmu/runstate.c:821
> 11 0x000055555585b19b in main (argc=21, argv=0x7fffffffe1c8, 
> envp=0x7fffffffe278)
>
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>   hw/net/virtio-net.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 02033be748..927a808654 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1397,7 +1397,9 @@ static void virtio_net_handle_rx(VirtIODevice *vdev, 
> VirtQueue *vq)
>   {
>       VirtIONet *n = VIRTIO_NET(vdev);
>       int queue_index = vq2q(virtio_get_queue_index(vq));
> -
> +    if (n->nic->peer_deleted) {
> +        return;


This needs to be fixed in the network core instead of virtio-net.

Thanks


> +    }
>       qemu_flush_queued_packets(qemu_get_subqueue(n->nic, queue_index));
>   }
>