Re: [Qemu-devel] qemu-kvm-0.11 regression, crashes on older guests with virtio network

[Anthony Liguori]

Mark McLoughlin wrote:
> >         tap_set_offload(csum: 1, tso4: 1, tso6: 1, ecn: 1)
> > being called and get an mtu of 1500 on virbr0 using his birdge.sh script.
> >
> > virtio_net_receive2 was trying to transfer a 1534 byte packet (1524 'size' + 10 
> > 'virtio_net_hdr')
> > and the guest only had 1524 bytes of space in its input descriptors.
> >     
>
> Okay, that sounds like a bug in Dustin's version of the guest virtio-net
> driver - if it is only supplying 1524 byte buffers, it should not be
> saying it supports the VIRTIO_NET_F_GUEST_TSO4 feature
>   

See:

commit 8eca6b1bc770982595db2f7207c65051572436cb
Author: aliguori <address@hidden>
Date:   Sun Apr 5 17:40:08 2009 +0000

   Fix oops on 2.6.25 guest (Rusty Russell)
  
   I believe this is behind the following:
   https://bugs.edge.launchpad.net/ubuntu/jaunty/+source/linux/+bug/331128
  
   virtio_pci in 2.6.25 didn't do feature negotiation correctly: it 
acked every
   bit.  Fortunately, we can detect this.
  
   Signed-off-by: Rusty Russell <address@hidden>
   Signed-off-by: Anthony Liguori <address@hidden>

It looks like Rusty's fix wasn't enough.  If I change virtio-net to only 
advertise F_MAC, we don't run into this problem.

Regards,

Anthony Liguori