On 11 April 2017 at 11:29, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On 11/04/17 11:16, Peter Maydell wrote: >> On 11 April 2017 at 11:08, Auger Eric <eric.auger@xxxxxxxxxx> wrote: >>> On 11/04/2017 12:05, Marc Zyngier wrote: >>>> On 10/04/17 16:17, Auger Eric wrote: >>>>> A (v1) -> B (v1 & v2): migration OK >>>>> B (v1 & v2) -> C (v1): migration NOK >>>> >>>> So what does IIDR report on B once the A->B migration has taken place? >>>> Does it report v2? >>> >>> yes that was the plan >> >> Hmm, the IIDR value shouldn't change across a migration I think. >> It's guest visible so the guest should see it still the same >> value even after migration. > > That's my worry. But we then have a problem when this VM migrates again. > How does userspace find out which ABI to use then? Userspace shouldn't need to care; the idea of this scheme is that if the kernel has to change its ABI then the kernel is what has to deal with the change. I think that means that if you can read the v1 format on input you have to output it too, though. thanks -- PMM
