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

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Date:   Wed, 27 Oct 2021 18:14:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     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>,
        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 27/10/21 18:08, Sean Christopherson wrote:
>> Right, so should we drop the "if (running)" check in this patch, at the same
>> time as it's adding the IN_GUEST_MODE check?
> LOL, I think we have a Three^WTwo Stooges routine going on.  This patch does
> remove avic_vcpu_is_running() and replaces it with the vcpu->mode check.  Or am
> I completely misunderstanding what your referring to?
> 
> -       if (avic_vcpu_is_running(vcpu)) {
> +       /*
> +        * Signal the doorbell to tell hardware to inject the IRQ if the vCPU
> +        * is in the guest.  If the vCPU is not in the guest, hardware will
> +        * automatically process AVIC interrupts at VMRUN.
> +        */
> +       if (vcpu->mode == IN_GUEST_MODE) {
>                  int cpu = READ_ONCE(vcpu->cpu);

Nevermind, I confused svm_deliver_avic_intr with avic_kick_target_vcpus, 
which anyway you are handling in patch 36.

Paolo