On Thu, 2025-08-14 at 16:54 +0800, hugo lee wrote: > 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. Simpler, cleaner, solves it for more use cases including when the interrupt *is* delivered to the PIC but just never services. And allows us to fix the VFIO INTx abomination and use the kernel's irqfd API properly... But that's a discussion for the qemu-devel list, I suppose.
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