From: hugo lee <cs.hugolee@gmail.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Sean Christopherson <seanjc@google.com>,
pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, Yuguo Li <hugoolli@tencent.com>
Subject: Re: [PATCH] KVM: x86: Synchronize APIC State with QEMU when irqchip=split
Date: Thu, 14 Aug 2025 16:54:48 +0800 [thread overview]
Message-ID: <CAAdeq_JQO2x=x07BwmDcTCU-WfKLW6kFk38881vbyUTehP+7gw@mail.gmail.com> (raw)
In-Reply-To: <f009b0c5dea8e50a7fa03056b177bcedcfd21132.camel@infradead.org>
On Wed, Aug 13, 2025 David Woodhouse <dwmw2@infradead.org> 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.
next prev parent reply other threads:[~2025-08-14 8:55 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-06 8:10 [PATCH] KVM: x86: Synchronize APIC State with QEMU when irqchip=split Yuguo Li
2025-08-06 18:20 ` Sean Christopherson
2025-08-07 8:03 ` hugo lee
2025-08-07 18:38 ` Sean Christopherson
2025-08-08 2:46 ` hugo lee
2025-08-11 16:32 ` Sean Christopherson
2025-08-12 9:39 ` David Woodhouse
2025-08-12 10:18 ` hugo lee
2025-08-12 10:08 ` hugo lee
2025-08-12 10:46 ` David Woodhouse
2025-08-12 11:50 ` hugo lee
2025-08-12 12:54 ` David Woodhouse
2025-08-13 9:30 ` hugo lee
2025-08-13 10:03 ` David Woodhouse
2025-08-14 8:54 ` hugo lee [this message]
2025-08-14 9:10 ` David Woodhouse
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