linux-kernel - Re: [PATCH 2/7] KVM: x86: inhibit APICv/AVIC when the guest and/or host changes either apic id or the apic base from their default values.

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Message-ID: <66b4d9d336884886d04d4d6dd5e517b2634ce625.camel@redhat.com>
Date:   Tue, 07 Jun 2022 10:53:42 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 2/7] KVM: x86: inhibit APICv/AVIC when the guest and/or
 host changes either apic id or the apic base from their default values.

On Tue, 2022-06-07 at 15:05 +0800, Chao Gao wrote:
> On Mon, Jun 06, 2022 at 09:08:24PM +0300, Maxim Levitsky wrote:
> > +       /*
> > +        * For simplicity, the APIC acceleration is inhibited
> > +        * first time either APIC ID or APIC base are changed by
> > the guest
> > +        * from their reset values.
> > +        */
> > +       APICV_INHIBIT_REASON_APIC_ID_MODIFIED,
> > +       APICV_INHIBIT_REASON_APIC_BASE_MODIFIED,
> > +
> > +
> 
> Remove one newline.
Will do.
> 
> > void kvm_apic_update_apicv(struct kvm_vcpu *vcpu)
> > @@ -2666,6 +2683,8 @@ static int kvm_apic_state_fixup(struct
> > kvm_vcpu *vcpu,
> >                         icr = __kvm_lapic_get_reg64(s->regs,
> > APIC_ICR);
> >                         __kvm_lapic_set_reg(s->regs, APIC_ICR2, icr
> > >> 32);
> >                 }
> > +       } else {
> > +               kvm_lapic_xapic_id_updated(vcpu->arch.apic);
> 
> Strictly speaking, this is needed only for "set" cases.
> 
True, thanks!


Best regards,
	Maxim Levitsky