linux-kernel - Re: [PATCH v2 1/5] KVM: LAPIC: Introduce interrupt delivery fastpath

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Message-ID: <CANRm+CzFgbuYY6t8E0OihXMzRV8ePjnoZPUPXxGcexbL8gKfEA@mail.gmail.com>
Date:   Thu, 23 Apr 2020 17:44:58 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Haiwei Li <lihaiwei@...cent.com>
Subject: Re: [PATCH v2 1/5] KVM: LAPIC: Introduce interrupt delivery fastpath

On Thu, 23 Apr 2020 at 17:41, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 23/04/20 11:35, Wanpeng Li wrote:
> >> Ok, got it now.  The problem is that deliver_posted_interrupt goes through
> >>
> >>         if (!kvm_vcpu_trigger_posted_interrupt(vcpu, false))
> >>                 kvm_vcpu_kick(vcpu);
> >>
> >> Would it help to make the above
> >>
> >>         if (vcpu != kvm_get_running_vcpu() &&
> >>             !kvm_vcpu_trigger_posted_interrupt(vcpu, false))
> >>                 kvm_vcpu_kick(vcpu);
> >>
> >> ?  If that is enough for the APICv case, it's good enough.
> > We will not exit from vmx_vcpu_run to vcpu_enter_guest, so it will not
> > help, right?
>
> Oh indeed---the call to sync_pir_to_irr is in vcpu_enter_guest.  You can
> add it to patch 3 right before "goto cont_run", since AMD does not need it.

Just move kvm_x86_ops.sync_pir_to_irr(vcpu)? How about the set pir/on
part for APICv and non-APICv part in fast_deliver_interrupt()?

    Wanpeng