On Thu, 2009-10-29 at 20:00 +0800, Scott Tsai wrote: > Excerpts from Mark McLoughlin's message of Thu Oct 29 17:16:43 +0800 2009: > > Assuming this is something like the virtio-net in 2.6.26, there was no > > receivable buffers support so (as Scott points out) it must be that > > we've read a packet from the tap device which is >1514 bytes (or >1524 > > bytes with IFF_VNET_HDR) but the guest has not supplied buffers which > > are large enough to take it > > > One thing to check is that the tap device is being initialized by > > qemu-kvm using TUNSETOFFLOAD with either zero or TUN_F_CSUM - i.e. GSO > > should not be enabled, because the guest cannot handle large GSO packets > > > Another possibility is that the MTU on the bridge in the host is too > > large and that's what's causing the large packets to be sent > > Using Dustin's image, I see: > virtio_net_set_features(features: 0x00000930) Hmm - 0x930 doesn't seem right. Is that 930 decimal, 0x3a2 hex? > 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 Cheers, 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
