On Wednesday 08 September 2010, Krishna Kumar2 wrote: > > On Wednesday 08 September 2010, Krishna Kumar2 wrote: > > > > The new guest and qemu code work with old vhost-net, just with > reduced > > > > performance, yes? > > > > > > Yes, I have tested new guest/qemu with old vhost but using > > > #numtxqs=1 (or not passing any arguments at all to qemu to > > > enable MQ). Giving numtxqs > 1 fails with ENOBUFS in vhost, > > > since vhost_net_set_backend in the unmodified vhost checks > > > for boundary overflow. > > > > > > I have also tested running an unmodified guest with new > > > vhost/qemu, but qemu should not specify numtxqs>1. > > > > Can you live migrate a new guest from new-qemu/new-kernel > > to old-qemu/old-kernel, new-qemu/old-kernel and old-qemu/new-kernel? > > If not, do we need to support all those cases? > > I have not tried this, though I added some minimal code in > virtio_net_load and virtio_net_save. I don't know what needs > to be done exactly at this time. I forgot to put this in the > "Next steps" list of things to do. I was mostly trying to find out if you think it should work or if there are specific reasons why it would not. E.g. when migrating to a machine that has an old qemu, the guest gets reduced to a single queue, but it's not clear to me how it can learn about this, or if it can get hidden by the outbound qemu. Arnd -- 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
