linux-kernel - Re: [PATCH 2/2] KVM: LAPIC: Don't need to clear IPI delivery status for x2apic

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Date:   Fri, 27 Mar 2020 17:27:04 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH 2/2] KVM: LAPIC: Don't need to clear IPI delivery status
 for x2apic

On Fri, 27 Mar 2020 at 17:07, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> Wanpeng Li <kernellwp@...il.com> writes:
>
> > From: Wanpeng Li <wanpengli@...cent.com>
> >
> > IPI delivery status field is not present for x2apic, don't need
> > to clear IPI delivery status for x2apic.
> >
> > Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> > ---
> >  arch/x86/kvm/lapic.c | 3 ++-
> >  arch/x86/kvm/x86.c   | 1 -
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index 88929b1..f6d69e2 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -1942,7 +1942,8 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
> >       }
> >       case APIC_ICR:
> >               /* No delay here, so we always clear the pending bit */
>
> 'Always' in the comment above now reads a bit odd, I'd suggest modifying
> it to 'Immediately clear Delivery Status field in xAPIC mode' - or just
> drop it altogeter.

Thank you for your review, I guess Paolo can do it when apply.

    Wanpeng

>
> > -             val &= ~(1 << 12);
> > +             if (!apic_x2apic_mode(apic))
> > +                     val &= ~(1 << 12);
> >               kvm_apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2));
> >               kvm_lapic_set_reg(apic, APIC_ICR, val);
> >               break;
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 495709f..6ced0e1 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -1562,7 +1562,6 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
> >               ((data & APIC_MODE_MASK) == APIC_DM_FIXED) &&
> >               ((u32)(data >> 32) != X2APIC_BROADCAST)) {
> >
> > -             data &= ~(1 << 12);
> >               kvm_apic_send_ipi(vcpu->arch.apic, (u32)data, (u32)(data >> 32));
> >               kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR2, (u32)(data >> 32));
> >               kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR, (u32)data);
>
> Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
>
> --
> Vitaly
>