Hi Peter, On 05/03/18 17:31, Peter Maydell wrote: > On 2 March 2018 at 12:26, Auger Eric <eric.auger@xxxxxxxxxx> wrote: >> Hi Marc, >> On 02/03/18 12:11, Marc Zyngier 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. >> >> That's because on the destination, the number of regs is less than on >> source, right? > > I think it fails because the KVM_REG_ARM_PSCI_VERSION register will be > in the migration state but not in the destination's list of registers: > the code in QEMU's target/arm/machine.c:cpu_post_load() function that > checks "register in their list but not ours: fail migration" will > catch this. Thank you for the pointer. Yes at the time I reviewed the patch and just focusing on the kernel code, this was not immediate to me. > > That also means that we will fail migration from a new kernel where > we've specifically asked for PSCI 0.2 to an old PSCI-0.2-only kernel > (because the KVM_REG_ARM_PSCI_VERSION reg will appear in the migration > stream even if its value is the one value that matches the old kernel > behaviour). I don't know if we care about that. Do you know when are we likely to force PSCI 0.2 on a new kernel? At which layer is the decision supposed to be made and on which criteria? Thanks Eric > > thanks > -- PMM > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
