linux-kernel - Re: [PATCH 3/3] KVM: x86: Trace all APICv inhibit changes and capture overall status

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Message-ID: <57c2d5d64f9d65e442744fa8b7f188ed3fd37c1c.camel@redhat.com>
Date:   Tue, 15 Mar 2022 16:48:12 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Chao Gao <chao.gao@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] KVM: x86: Trace all APICv inhibit changes and
 capture overall status

On Tue, 2022-03-15 at 22:42 +0800, Chao Gao wrote:
> On Fri, Mar 11, 2022 at 04:35:17AM +0000, Sean Christopherson wrote:
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -9053,15 +9053,29 @@ bool kvm_apicv_activated(struct kvm *kvm)
> > }
> > EXPORT_SYMBOL_GPL(kvm_apicv_activated);
> > 
> > +
> 
> stray newline.
> 
> > +static void set_or_clear_apicv_inhibit(unsigned long *inhibits,
> > +				       enum kvm_apicv_inhibit reason, bool set)
> > +{
> > +	if (set)
> > +		__set_bit(reason, inhibits);
> > +	else
> > +		__clear_bit(reason, inhibits);
> > +
> > +	trace_kvm_apicv_inhibit_changed(reason, set, *inhibits);
> 
> Note that some calls may not toggle any bit. Do you want to log them?
> I am afraid that a VM with many vCPUs may get a lot of traces that actually
> doesn't change inhibits.

I also think so.

Best regards,
	Maxim Levitsky

> 
> Anyway, this series looks good to me.
>