Re: kvm-hint-dedicated requires host CPU passthrough?
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.
Wim: Can you let us know what the original intention of checking for
cpu-passthrough was?
Thanks,
Stefan
Attachments:
- signature.asc (application/pgp-signature — 488 bytes)