On Wed, Nov 19, 2014 at 03:20:07PM +0100, Juan Quintela wrote: > 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
Not added mostly because there's no point: CPU vendors would much rather sell you a new CPU :) Features could be removed because of some errata? -- MST
