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Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index |
Date: |
Wed, 14 Jun 2017 10:01:49 -0300 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, Jun 14, 2017 at 01:26:44PM +0200, Paolo Bonzini wrote:
>
>
> 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.
No, KVM really uses the VCPU _index_ for HV_X64_MSR_VP_INDEX:
kvm_hv_get_msr():
case HV_X64_MSR_VP_INDEX: {
int r;
struct kvm_vcpu *v;
kvm_for_each_vcpu(r, v, vcpu->kvm) {
if (v == vcpu) {
data = r;
break;
}
}
break;
}
--
Eduardo
- [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, (continued)
- [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/06
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Eduardo Habkost, 2017/06/13
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Paolo Bonzini, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Igor Mammedov, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/15
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Paolo Bonzini, 2017/06/15
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Igor Mammedov, 2017/06/15
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/15
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Eduardo Habkost, 2017/06/18
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index,
Eduardo Habkost <=
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Igor Mammedov, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Paolo Bonzini, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Eduardo Habkost, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Paolo Bonzini, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Igor Mammedov, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Eduardo Habkost, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Eduardo Habkost, 2017/06/14
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Paolo Bonzini, 2017/06/15
- Re: [Qemu-devel] [PATCH 05/23] hyperv: ensure VP index equal to QEMU cpu_index, Roman Kagan, 2017/06/15