On 14/06/2017 13:25, Roman Kagan wrote: >> The problem with that is that it will break as soon as we create >> VCPUs in a different order. Unsolvable on hosts that don't allow >> HV_X64_MSR_VP_INDEX to be set, however. > Right, thanks for putting together a detailed explanation. > > This was a thinko back then, not to have HV_X64_MSR_VP_INDEX maintained > by QEMU. I'm going to post a patch to KVM fixing that. > > Meanwhile QEMU needs a way to maintain its notion of vp_index that is > 1) in sync with kernel's notion > 2) also with kernels that don't support setting the msr > 3) persistent across migrations > > cpu_index looked like a perfect candidate. >
What you want is the APIC id, which _is_ cpu_index but may not be in the future. But the APIC id is also the KVM vcpu_id, so there's no need to have VP_INDEX maintained by QEMU. Paolo
