On Wed, Jun 10, 2009 at 06:30:16PM +0100, Paul Brook wrote: > On Wednesday 10 June 2009, Michael S. Tsirkin wrote: > > On Wed, Jun 10, 2009 at 05:46:03PM +0100, Paul Brook wrote: > > > > > If you can't create an identical machine from scratch then I don't > > > > > consider snapshot/migration to be a useful feature. i.e. as soon as > > > > > you shutdown and restart the guest it is liable to break anyway. > > > > > > > > Why is liable to break? > > > > > > A VM booted on an old version of qemu and migrated to a new version will > > > behave differently to a the same VM booted on a new version of qemu. > > > > It will behave identically. That's what the patch does: discover > > how did the device behave on old qemu, and make it behave the same way > > on new qemu. > > You're missing the point. After doing a live migration from old-qemu to new- > qemu, there is no snapshot to load. We need to be able to shutdown the guest, > kill qemu (without saving a snapshot), then start qemu with the exact same > hardware. Yes, I see how this would sometimes be useful. So this feature request would mean that we need a flag to disable msix in virtio net. I think we can agree that hardware can change across reboots. It can with real hardware and it happens without guest doing anything. > If we can't start a new qemu with the same hardware configuration then we > should not be allowing migration or loading of snapshots. > > Paul OK, so I'll add an option in virtio-net to disable msi-x, and such an option will be added in any device with msi-x support. Will that address your concern? -- MST -- 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
