Re: [Qemu-devel] [PATCH] vhost_net: initialize acked_features to a safe value during ack

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

On Wed, Sep 03, 2014 at 12:54:03PM +0400, Andrey Korolyov wrote:
> On Wed, Sep 3, 2014 at 12:52 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Wed, Sep 03, 2014 at 02:25:30PM +0800, Jason Wang wrote:
> >> commit 2e6d46d77ed328d34a94688da8371bcbe243479b (vhost: add
> >> vhost_get_features and vhost_ack_features) removes the step that
> >> initializes the acked_features to backend_features. This will result an
> >> unexpected value of acked_features which may fail the features setting of
> >> vhost. This patch fixes it by recover this step.
> >>
> >> Cc: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
> >> Cc: Andrey Korolyov <andrey@xdel.ru>
> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
> >> Cc: qemu-stable@nongnu.org
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >
> > OK I get it and it's correct, but I think it's better to
> > put the initialization in core vhost code.
> > Patch sent, could you confirm that it works for you please?
> >
> >> ---
> >>  hw/net/vhost_net.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> >> index f87c798..b1d4b1f 100644
> >> --- a/hw/net/vhost_net.c
> >> +++ b/hw/net/vhost_net.c
> >> @@ -115,6 +115,7 @@ unsigned vhost_net_get_features(struct vhost_net *net, unsigned features)
> >>
> >>  void vhost_net_ack_features(struct vhost_net *net, unsigned features)
> >>  {
> >> +    net->dev.acked_features = net->dev.backend_features;
> >>      vhost_ack_features(&net->dev, vhost_net_get_feature_bits(net), features);
> >>  }
> >>
> >> --
> >> 1.8.3.1
> 
> Yes, this patch fixes both issues with vhost subsystem for me.

OK, applied, thanks!
But let's hack on the assert a bit more: apparently something
is wrong with the userspace fallback: after init failure,
it should never trigger, and it does.

-- 
MST