On 18/02/2016 10:24, Greg Kurz wrote: > 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 ?
Yes :) If you post a new series with this idea, I'll test it to be sure we don't introduce new problems. Laurent
