linux-kernel - Re: [PATCH v3] KVM: x86/vmx: Suppress posted interrupt notification when CPU is in host

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Message-ID: <YzU0KyTx2SPRadTm@gao-cwp>
Date:   Thu, 29 Sep 2022 13:59:07 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <jon@...anix.com>, <kevin.tian@...el.com>, <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3] KVM: x86/vmx: Suppress posted interrupt notification
 when CPU is in host

On Wed, Sep 28, 2022 at 07:16:03PM +0800, Chao Gao wrote:
>@@ -10538,6 +10547,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> 
> 	vcpu->mode = OUTSIDE_GUEST_MODE;
> 	smp_wmb();
>+	/*
>+	 * Suppress notification when CPU is OUTSIDE_GUEST_MODE to avoid
>+	 * wasting time on handling interrupts. A notification to host/kvm
>+	 * just indicates some interrupts are posted for a vCPU. Since KVM
>+	 * always syncs pending interrupts in PIR to vAPIC IRR before guest
>+	 * entry (in ->sync_pir_to_irr()), notification isn't needed.
>+	 *
>+	 * Do this even if apicv is disabled for simplicity.
>+	 */
>+	if (kvm_lapic_enabled(vcpu))
>+		static_call_cond(kvm_x86_pi_suppress_notification)(vcpu, true);

I missed the other kvm's setting vcpu->mode to OUTSIDE_GUEST_MODE in
this function (a few lines above). Will fix it in v4.

> 
> 	/*
> 	 * Sync xfd before calling handle_exit_irqoff() which may
>
>base-commit: 372d07084593dc7a399bf9bee815711b1fb1bcf2
>-- 
>2.25.1
>