Re: [PATCH v6 05/36] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock migration

On Sat, Jul 25, 2026, David Woodhouse wrote:
> On Fri, 2026-07-24 at 14:17 -0700, Sean Christopherson wrote:
> > On Fri, Jul 03, 2026, David Woodhouse wrote:
> > > +4.145 KVM_GET_CLOCK_GUEST
> > > +----------------------------
> > > +
> > > +:Capability: none
> > 
> > Why not add a CAP?  The check in the subsequent selftest is quite gross.
> 
> Because nobody would ever use it in practice anyway. 

Yes, the selftest will.

> Even if the ioctl is present, you *still* have to try it and fall back to the
> old method because there are ways that a *guest* can force master clock mode
> off.

That's totally fine, but userspace, especially for selftests, needs a way to
know the ioctl exists and _should_ work.