Re: [Qemu-devel] [PATCH for-1.6] virtio: clear signalled_used_valid when switching from dataplane

[Stefan Hajnoczi]

On Mon, Aug 12, 2013 at 11:18 AM, Michael S. Tsirkin <address@hidden> wrote:
> On Mon, Aug 12, 2013 at 11:08:09AM +0200, Stefan Hajnoczi wrote:
>> When the dataplane thread stops, its vring.c implementation synchronizes
>> vring state back to virtio.c so we can continue emulating the virtio
>> device.
>>
>> This patch ensures that virtio.c's signalled_used_valid flag is reset so
>> that we do not suppress guest notifications due to stale signalled_used
>> values.
>>
>> Suggested-by: Kevin Wolf <address@hidden>
>> Signed-off-by: Stefan Hajnoczi <address@hidden>
>
> Good point
>
> Reviewed-by: Michael S. Tsirkin <address@hidden>
>
> and we also need this for vhost.c right?

I think vhost is not affected by this because virtio.c clears the
signalled_used_valid flag when the device is reset.  Since vhost_net
does not transition back and forth between userspace virtio and vhost
(without a device reset), there is no need to reset the flag.

Stefan