linux-kernel - Re: [PATCH] svm: Fix AVIC incomplete IPI emulation

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Date:   Wed, 13 Mar 2019 03:08:03 +0000
From:   "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>
To:     Oren Twaig <oren@...lemp.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] svm: Fix AVIC incomplete IPI emulation

Oren,

On 3/11/19 6:38 PM, Suthikulpanit, Suravee wrote:
> However, looking a bit more closely, I notice the logic in svm_deliver_avic_intr()
> should also have been changed from kvm_vcpu_wake_up() to kvm_vcpu_kick()
> since the latter will result in clearing the IRR bit for the IPI vector
> when trying to send IPI as part of the following call path.
> 
>     vcpu_enter_guest()
>       |-- inject_pending_event()
>         |-- kvm_cpu_get_interrupt()
>           |--  kvm_get_apic_interrupt()
>             |-- apic_clear_irr()
>             |-- apic_set_isr()
>             |-- apic_update_ppr() ....
> 
> Please see the patch below.
> 
> Not sure if this would address the problem you are seeing.
> 
> Thanks,
> Suravee
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 24dfa6a93711..d2841c3dbc04 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -5219,11 +5256,13 @@ static void svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
>           kvm_lapic_set_irr(vec, vcpu->arch.apic);
>           smp_mb__after_atomic();
> 
> -       if (avic_vcpu_is_running(vcpu))
> +       if (avic_vcpu_is_running(vcpu)) {
>                   wrmsrl(SVM_AVIC_DOORBELL,
>                          kvm_cpu_get_apicid(vcpu->cpu));
> -       else
> -               kvm_vcpu_wake_up(vcpu);
> +       } else {
> +               kvm_make_request(KVM_REQ_EVENT, vcpu);
> +               kvm_vcpu_kick(vcpu);
> +       }
>    }
> 
>    static void svm_ir_list_del(struct vcpu_svm *svm, struct amd_iommu_pi_data *pi)

Please ignore the part mentioned above. The current implementation should already be fine.

Suravee