[Qemu-devel] Re: [SeaBIOS] [PATCH 0/8] option rom loading overhaul.

[Sebastian Herbszt]

Gerd Hoffmann wrote:
> On 12/18/09 17:42, Anthony Liguori wrote:
> > > Do we need to do something for -M pc-0.11? Like loading the pci roms
> > > via fw_cfg too so the guest doesn't see the new pci rom bar?
> >
> > Yes, we do. We can fix that problem as a stable-0.12 update though.
> > Right now, migration with pc-0.11 is broken in other areas too.
>
> Ok.  When it is fine to defer this to stable-0.12 then I have no 
> objections to merge it for 0.12 (assuming the seabios folks ack+merge 
> the seabios changes).

0.12 will contain known regressions?

> Note that I'll be offline for x-mas and newyear starting tomorrow, so I 
> will not be able to work on that until January.
>
> > It's really unclear to me the best way to handle live migration. The
> > rom_offset is not enough because unfortunately it's not stable after
> > invocations of qemu. I think we're going to have to actually save the
> > some contents with the PCIDevices.
>
> With hotplug this will become a issue indeed.
>
> > > Is 0.11 -> 0.12 migration supposed to work? That could become quite
> > > nasty too. But maybe that is impossible anyway due to the switch to
> > > seabios?
> >
> > In theory, it should work. SeaBIOS should not be a guest visible change
> > because the guest should not depend on what BIOS we're using.

If SeaBIOS would not have any regressions compared to Bochs BIOS then maybe.

> Indeed.  In theory even the switch of the option rom loading should work 
> just fine.  After migration old bios and roms are still in memory, the 
> next reboot will be the world switch to new seabios, new roms, new way 
> to deploy roms and everything.

Automagical "world switch" on reboot sounds like a nightmare. The VM environment
should be stable during reboots and only change if requested by the user.

- Sebastian