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@xxxxxxxxxxxxxxx> > Signed-off-by: Anthony Liguori <aliguori@xxxxxxxxxx> > > 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? Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
