Qin Chuanyu
2013-Oct-14 08:19 UTC
Re: Is fallback vhost_net to qemu for live migrate available?
On 2013/8/30 0:08, Anthony Liguori wrote:> Hi Qin, > > KVM and Xen represent memory in a very different way. KVM can only > track when guest mode code dirties memory. It relies on QEMU to track > when guest memory is dirtied by QEMU. Since vhost is running outside > of QEMU, vhost also needs to tell QEMU when it has dirtied memory. > > I don't think this is a problem with Xen though. I believe (although > could be wrong) that Xen is able to track when either the domain or > dom0 dirties memory. > > So I think you can simply ignore the dirty logging with vhost and it > should Just Work. >Xen track guest's memory when live migrating as what KVM did (I guess it rely on EPT),it couldn't mark dom0's dirty memory automatically. I did the same dirty log with vhost_net but instead of KVM's api with Xen's dirty memory interface,then live migration work. -------------------------------------------------------------------- There is a bug on the Xen live migration when using qemu emulate nic(such as virtio_net). current flow: xc_save->dirty memory copy->suspend->stop_vcpu->last memory copy stop_qemu->stop_virtio_net save_qemu->save_virtio_net it means virtio_net would dirty memory after the last memory copy. I have test it both vhost_on_qemu and virtio_net in qemu,there are same problem, the update of vring_index would be mistake and lead network unreachable. my solution is: xc_save->dirty memory copy->suspend->stop_vcpu->stop_qemu ->stop_virtio_net->last memory copy save_qemu->save_virtio_net Xen's netfront and netback disconnect and flush IO-ring when live migrate,so it is OK. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel