On Thu, 18 Feb 2016 12:06:39 +0530 Amit Shah <amit.s...@redhat.com> wrote:
> On (Thu) 18 Feb 2016 [13:50:25], David Gibson wrote: > > On Wed, Feb 17, 2016 at 05:06:43PM +0100, Greg Kurz wrote: > > > Since the addition of the configuration section in QEMU 2.4, it is > > > impossible > > > to migrate a pseries-2.3 machine back to QEMU 2.3. > > > > > > This patch makes it possible thanks to a new machine property which > > > allows to > > > disable configuration section submission. > > > > > > To disable submission, just add: > > > > > > -machine suppress-config-section=on > > > > > > Alternatively, if the target QEMU version isn't known at startup, this can > > > be done later from the QEMU monitor with: > > > > > > qom-set /machine suppress-config-section on > > > > > > This property won't be automatically set for pseries-2.3 because it would > > > then break backward migration to QEMU 2.4. If automatic behaviour is > > > needed, > > > it is up to the tooling to handle this. > > > > As noted elsewhere, I'd actually be ok with enabling it for > > pseries-2.3. Basically we have to chose whether to work against qemu > > 2.3 or 2.4 out of the box, we can't have both, and it sounds like qemu > > 2.3 is more widely deployed than qemu 2.4. > > > > > > > > Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com> > > > > Reviewed-by: David Gibson <da...@gibson.dropbear.id.au> > > > > I'm not sure whose tree these need to go in via. > > I'd like to see Juan's ack, and I'm fine if you take it via your tree. > > > > Amit > Hi, I also have another option I'd like to submit. Basically, this would be: - introduce a enforce-config-section machine property which allows to override the savevm_state.skip_configuration flag - update pseries-2.3 to skip configuration section by default (like it should have been done in the beginning) It would fix migration from/to QEMU 2.3 of pseries-2.3 without manual intervention. Only migration to/from QEMU 2.4/2.5 would require manual use of the enforce-config-section. Laurent, is this what you had in mind ? -- Greg