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

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Date:   Tue, 15 Mar 2022 22:42:50 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     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 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.

Anyway, this series looks good to me.