linux-kernel - Re: [patch 2/2] x86/kvm: Sanitize kvm_async_pf_task

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Date:   Sat, 07 Mar 2020 21:08:56 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, KVM <kvm@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [patch 2/2] x86/kvm: Sanitize kvm_async_pf_task_wait()

Andy Lutomirski <luto@...nel.org> writes:
> On Sat, Mar 7, 2020 at 7:52 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>> WHAT? That's fundamentally broken. Can you point me to the code in
>> question?
>
> I think Paolo said so in a different thread, but I can't Let me see if
> I can find it:
>
> kvm_pv_enable_async_pf()
>   kvm_clear_async_pf_completion_queue()
>
> but that doesn't actually seem to send #PF.  So maybe I'm wrong.
>
> I will admit that, even after reading the host code a few times, I'm
> also not convinced that wakeups don't get swallowed on occasion if
> they would have been delivered at times when it's illegal.

I gave up trying to decode it. I wait for the kvm wizards to answer all
our nasty questions :)

Thanks,

        tglx