"Michael S. Tsirkin" <m...@redhat.com> wrote: > On Tue, Nov 24, 2009 at 12:39:50PM +0200, Dor Laor wrote: >> On 11/23/2009 02:15 PM, Juan Quintela wrote: >>> Dor Laor<dl...@redhat.com> wrote: >>>> > In the last couple of days we discovered some issues regarding stable >>>> > ABI and the robustness of the live migration protocol. Let's just jump >>>> > right into it, ordered by complexity: >>>> > >>>> > 1. Control*every* feature exposed to the guest by qemu cmdline: >>>> > >>>> > While thinking on cross version migration, and reviewing some >>>> > patches, I noticed that there are many times that we use feature >>>> > bits >>>> > in order to expose functionality for the guest driver - example: >>>> > VIRTIO_BLK_F_BARRIER, but we do not control it from qemu cmdline. >>> In my opinion this is madness, qemu command line is already too >>> complicated. I agree with anthony to put it in the command line. >> >> Qemu's cmdline is currently our config file.. Actually there is nothing >> wrong with it. Human users shouldn't be interested with these changes >> and management software should not have problem manipulating it. >> We do need flexibility of controlling our features like any other >> software component. >> >>> I will go further, and think that this kind of issues should be put into >>> the machine type. >>> >>> If you start qemu with -M pc-0.10, it should save the state in a 0.10 >>> compatible way (that don't happens at the moment, but it should work >>> that way). >> >> That's the idea - to keep it part of qdev and by default use it with -M. > > I think we want to keep these things separate: > machine description should be for things that > are both guest visible and not changeable by guest, > so it absolutely must stay constant as long as guest > it alive.
That is exactly what we need here, that version of the savevm protocol for each device is the same. Later, Juan.
