On Sat, Jun 03, 2017 at 09:36:23AM +0200, Laszlo Ersek wrote: > On 06/02/17 17:45, Laszlo Ersek wrote: > > > The patches can cause linker/loader breakage when old firmware is booted > > on new QEMU. However, that's no problem (it's nothing new), the next > > release of QEMU should bundle the new firmware binaries as always. > > Dave made a good point (which I should have realized myself, really!), > namely if you launch old fw on old qemu, then migrate the guest to a new > qemu and then reboot the guest on the target host, within the migrated > VM, things will break. > > So that makes this approach dead in the water. > > Possible mitigations I could think of: > - Make it machine type dependent. Complicated (we don't usually bind > ACPI generation to machine types) and wouldn't help existing devices. > - Let the firmware negotiate these extensions. Very complicated (new > fw-cfg files are needed for negotiation) and wouldn't help existing devices.
This last option *shouldn't* be complicated. If it is something's wrong. Maybe we made a mistake when we added etc/smi/*features*. It's not too late to move these to etc/*features* for new machine types if we want to and if you can do the firmware work. Then you'd just take out a bit and be done with it. I don't insist on doing the ACPI thing now but I do think infrastructure for negotiating extensions should be there. -- MST
