Re: [PATCH v4 2/2] KVM: move vcpu id checking to archs

From: Igor Mammedov
Date: Fri Apr 22 2016 - 07:20:10 EST


On Fri, 22 Apr 2016 11:25:38 +0200
Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> wrote:

> Hi Radim !
>
> On Thu, 21 Apr 2016 19:36:11 +0200
> Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx> wrote:
>
> > 2016-04-21 18:45+0200, Greg Kurz:
> > > On Thu, 21 Apr 2016 18:00:19 +0200
> > > Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx> wrote:
> > >> 2016-04-21 16:20+0200, Greg Kurz:
[...]
> > > maybe later
> > > if we have other scenarios where vcpu ids need to cross the limit ?
> >
> > x86 is going to have that soon too -- vcpu_id will be able to range from
> > 0 to 2^32-1 (or 2^31), but MAX_CPUS related data structures probably
> > won't be improved to actually scale, so MAX_CPUS will remain lower.
> >
That's not true, x86 is going to stick with KVM_MAX_VCPUS/qemu's max_cpus,
the only thing that is going to change is that max supported APIC ID
value will be in range 0 to 2^32-1 vs current 8bit one
and since APIC ID is not vcpu_id so it won't affect vcpu_id.

>
> Do you have some pointers to share so that we can see the broader picture ?
>
> Thanks !
>
> --
> Greg
>
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