linux-kernel - Re: [PATCH v2 3/5] KVM: SVM: fix race between interrupt delivery and AVIC inhibition

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Message-ID: <2fdc37d84764c2fe1bd4063a2956b2101936f66a.camel@redhat.com>
Date:   Wed, 05 Jan 2022 14:15:32 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joerg Roedel <joro@...tes.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v2 3/5] KVM: SVM: fix race between interrupt delivery
 and AVIC inhibition

On Wed, 2022-01-05 at 12:54 +0100, Paolo Bonzini wrote:
> On 1/5/22 12:03, Maxim Levitsky wrote:
> > > Hmm, my preference would be to keep the "return -1" even though apicv_active must
> > > be rechecked.  That would help highlight that returning "failure" after this point
> > > is not an option as it would result in kvm_lapic_set_irr() being called twice.
> > I don't mind either - this will fix the tracepoint I recently added to report the
> > number of interrupts that were delivered by AVIC/APICv - with this patch,
> > all of them count as such.
> 
> Perhaps we can move the tracepoints in the delivery functions.  This 
> also makes them more precise in the rare case where apicv_active changes 
> in the middle of the function.

That is what I was thinking to do as well, but I don't mind returning the 'return -1' as well.
Best regards,
	Maxim Levitsky

> 
> Paolo
>