kvm-hint-dedicated requires host CPU passthrough?
Wim ten Have
wim.ten.have at oracle.com
Mon Jun 29 16:00:08 UTC 2020
Oh, I also see that my claws-mail filters are in chaos and that there's
additional email to this mail-thread.
On Thu, 21 May 2020 16:14:34 +0100
Stefan Hajnoczi <stefanha at redhat.com> wrote:
> On Wed, May 20, 2020 at 07:23:32PM +0200, Paolo Bonzini wrote:
> > On 20/05/20 19:13, Stefan Hajnoczi wrote:
> > > Hi,
> > > libvirt refuses to set KVM_HINTS_DEDICATED when the CPU model is not
> > > host-passthrough.
> > >
> > > Is there a reason for this limitation?
> > >
> > > My understanding is that KVM_HINTS_DEDICATED means the vCPU is pinned to
> > > a host CPU that is not shared with other tasks. Any KVM vCPU should be
> > > able to support this feature, regardless of whether host-passthrough is
> > > used or not.
> > Perhaps it's because KVM_HINTS_DEDICATED enables mwait passthrough, and
> > the details of mwait vary per CPU model?
> KVM_HINTS_DEDICATED (now known as KVM_HINTS_REALTIME) is also used by
> cpuidle-haltpoll. In that case we don't care about mwait.
> CPU passthrough can prevent live migration, so I think we should relax
> this check, if possible.
I agree, the check for <cpu mode='host-passthrough'/> should be relaxed.
> Wim: Can you let us know what the original intention of checking for
> cpu-passthrough was?
>From our, my proposed, point of view it was. But that seems silly indeed.
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