On 2 March 2018 at 11:11, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On Fri, 02 Mar 2018 10:44:48 +0000, > Auger Eric wrote: >> I understand the get/set is called as part of the migration process. >> So my understanding is the benefit of this series is migration fails in >> those cases: >> >> >=0.2 source -> 0.1 destination >> 0.1 source -> >=0.2 destination > > It also fails in the case where you migrate a 1.0 guest to something > that cannot support it. I think it would be useful if we could write out the various combinations of source, destination and what we expect/want to have happen. My gut feeling here is that we're sacrificing exact migration compatibility in favour of having the guest automatically get the variant-2 mitigations, but it's not clear to me exactly which migration combinations that's intended to happen for. Marc? If this wasn't a mitigation issue the desired behaviour would be straightforward: * kernel should default to 0.2 on the basis that that's what it did before * new QEMU version should enable 1.0 by default for virt-2.12 and 0.2 for virt-2.11 and earlier * PSCI version info shouldn't appear in migration stream unless it's something other than 0.2 But that would leave some setups (which?) unnecessarily without the mitigation, so we're not doing that. The question is, exactly what *are* we aiming for? thanks -- PMM _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
