linux-kernel - Re: [PATCH v2 35/43] KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode

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Date:   Mon, 25 Oct 2021 16:26:17 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Anup Patel <anup.patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Atish Patra <atish.patra@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 35/43] KVM: SVM: Signal AVIC doorbell iff vCPU is in
 guest mode

On 09/10/21 04:12, Sean Christopherson wrote:
> +	 */
> +	if (vcpu->mode == IN_GUEST_MODE) {
>   		int cpu = READ_ONCE(vcpu->cpu);
>   
>   		/*
> @@ -687,8 +692,13 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
>   		if (cpu != get_cpu())
>   			wrmsrl(SVM_AVIC_DOORBELL, kvm_cpu_get_apicid(cpu));
>   		put_cpu();
> -	} else
> +	} else {
> +		/*
> +		 * Wake the vCPU if it was blocking.  KVM will then detect the
> +		 * pending IRQ when checking if the vCPU has a wake event.
> +		 */
>   		kvm_vcpu_wake_up(vcpu);
> +	}
>   

Does this still need to check the "running" flag?  That should be a 
strict superset of vcpu->mode == IN_GUEST_MODE.

Paolo