Paolo Bonzini <pbonz...@redhat.com> wrote: > On 19/11/2014 15:03, Juan Quintela wrote: >> Paolo Bonzini <pbonz...@redhat.com> wrote: >>> On 19/11/2014 14:49, Juan Quintela wrote: >>>>>> Real hardware lets users update firmware and so should virtual hardware. >>>> But you can hibernate your laptop, update the firmware, and reboot? >>>> Where the change can be anyting, like moving from traditional BIOS to >>>> UEFI? >>> >>> Wait wait wait. I totally cannot follow. What would be the equivalent >>> in QEMU? >> >> qemu-2.0 -M pc-2.0 >> >> migrate to disk/s3/s4 >> >> upgrade qemu >> >> qemu-2.2 -M pc-2.0 >> >> try interesting variation of s3/s4/migration to disk. Migration to disk >> should work (we migrate BIOS ROM blocks, enphasis on ROM), s3 perhaps >> (machine needs to be saved to disk), s4 ..... depends how it ends being >> done. > > Ok, got it. S3 + migrate to disk should work. > > S4 probably would work, but I think it would work on a real system too > as long as you update software and not hardware (e.g. changing the > motherboard would change the MAC address of the on-board NIC, for example). > > Consider the similar case on real hardware: > > boot > update microcode RPM > s4 > turn on > > CPU microcode is installed early by the kernel, before looking for a > hibernation image to resume from, so the CPU microcode after resume from > S4 is different from the microcode at the time you suspended to disk. > This probably would work.
I am not an expert of cpu microcode, but I would assume that changes there tend to be minimal, no? And anyways, I wouldn't expect to introduce/remove features like NX (i.e. visible by the guest) on a microcode update? Later, Juan. > Paolo
