On 06/10/2014 06:10 PM, Michael S. Tsirkin wrote: > On Tue, Jun 10, 2014 at 11:50:33AM +0530, Amit Shah wrote: >> On (Tue) 20 May 2014 [14:01:44], Jason Wang wrote: >>> It's hard to track all mac addresses and their configurations (e.g >>> vlan or ipv6) in qemu. Without this information, it's impossible to >>> build proper garp packet after migration. The only possible solution >>> to this is let guest (who knows all configurations) to do this. >>> >>> So, this patch introduces a new readonly config status bit of virtio-net, >>> VIRTIO_NET_S_ANNOUNCE which is used to notify guest to announce >>> presence of its link through config update interrupt.When guest has >>> done the announcement, it should ack the notification through >>> VIRTIO_NET_CTRL_ANNOUNCE_ACK cmd. This feature is negotiated by a new >>> feature bit VIRTIO_NET_F_ANNOUNCE (which has already been supported by >>> Linux guest). >>> >>> During load, a counter of announcing rounds is set so that after the vm is >>> running it can trigger rounds of config interrupts to notify the guest to >>> build >>> and send the correct garps. >> Live migration is supposed to be transparent to guests. >> >> Doing things this way makes the guest involved in live migration. >> It's not desirable. > I'm not sure there's a problem. > As long as guest doesn't use networking, it does not > need to be involved. If guest does want to use networking, > it needs to be involved, but then it's accessing the > device anyway. > >> For networking, this may well be not possible. >> Are there any ways of doing this w/o involving the guest that have >> been considered? >> >> >> Amit > Since we don't know guest addresses, this looks like the only way to me. >
Yes and this method were also used by Xen and HyperV.
