linux-kernel - Re: [PATCH 2/3] KVM: x86: Fix a semi theoretical bug in kvm_arch_async_page_present

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Message-ID: <aQPKbmJGKFvMX56f@google.com>
Date: Thu, 30 Oct 2025 13:28:30 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: mlevitsk@...hat.com
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org, 
	Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] KVM: x86: Fix a semi theoretical bug in kvm_arch_async_page_present_queued

On Thu, Oct 30, 2025, mlevitsk@...hat.com wrote:
> On Mon, 2025-10-27 at 08:00 -0700, Sean Christopherson wrote:
> > On Tue, Sep 23, 2025, Sean Christopherson wrote:
> > > On x86, the "page ready" IRQ is only injected from vCPU context, so AFAICT nothing
> > > is guarnateed wake the vCPU in the above sequence.
> > 
> > Gah, KVM checks async_pf.done instead of the request.  So I don't think there's
> > a bug, just weird code.
> 
> Hi!
> 
> Note that I posted a v2 of this patch series.

I got 'em, and looked at them in depth (which is how I figured out the above
weirdness with async_pf.done).  They're sitting in my "for_next" folder, I just
haven't spent any time on applying+testing upstream patches this week (I expect
to get to your series tomorrow, or early next week).

> Do I need to drop this patch or its better to keep it (the patch should still
> be correct, but maybe an overkill I think).

It's probably overkill, but there's no real downside, so I'm inclined to apply
the v2 version (and am planning on doing so).