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

[Dustin Kirkland <kirkland@canonical.com>]

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On Thu, 2009-10-29 at 14:25 +0000, Mark McLoughlin wrote:
> On Thu, 2009-10-29 at 09:11 -0500, Anthony Liguori wrote:
> > 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 <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162>
> > 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 <rusty@rustcorp.com.au>
> >     Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
> > 
> > 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.
> 
> If it's not acking VBAD_FEATURE, then it doesn't sound like the same
> issue
> 
> It's also not acking e.g. MRG_RXBUF, which suggests that it is
> selectively acking features, and choosing to ack TSO4
> 
> A quick look through the guest driver code should clear up the
> confusion. Dustion, got a pointer?

Hi Mark,

I'm currently testing Scott's patch above.

In the mean time, Hardy's kernel is in git here:

http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy.git;a=summary

Thanks,
:-Dustin

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