Re: [PATCH] KVM: x86: Synchronize APIC State with QEMU when irqchip=split

[hugo lee]

On Wed, Aug 13, 2025 David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote:
>
> On Wed, 2025-08-13 at 17:30 +0800, hugo lee wrote:
> >
> > Sorry for the misleading, what I was going to say is
> > do only cpu_synchroniza_state() in this new userspace exit reason
> > and do nothing on the PIT.
> > So QEMU will ignore the PIT as the guests do.
> >
> > The resample is great and needed, but the synchronization
> > makes more sense to me on this question.
>
> So if the guest doesn't actually quiesce the PIT, QEMU will *still*
> keep waking up to waggle the PIT output pin, it's just that QEMU won't
> bother telling the kernel about it?

Yes, just as guests wish.
This could eliminate the most performance loss.

But I guess resample is more acceptable.