linux-kernel - Re: [PATCH 0/2] KVM: VMX: Avoid RDMSRs in PI x2APIC checks

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Message-ID: <d9d59280-0f68-6af0-82d0-87d1eda69a07@redhat.com>
Date:   Mon, 18 Jan 2021 19:24:23 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, luferry <luferry@....com>
Subject: Re: [PATCH 0/2] KVM: VMX: Avoid RDMSRs in PI x2APIC checks

On 15/01/21 23:03, Sean Christopherson wrote:
> Resurrect a patch[*] from over a year ago to avoid RDMSR in a fairly hot
> path in KVM's posted interrupt support.  Note, in my response to that
> patch, I suggested checking x2apic_supported() as well as x2apic_mode.  I
> have no idea why I suggested that; unless I'm missing something,
> x2apic_mode can never be set if x2apic_supported() is false.
> 
> [*] https://lkml.kernel.org/r/20190723130608.26528-1-luferry@163.com/
> 
> Sean Christopherson (2):
>    x86/apic: Export x2apic_mode for use by KVM in "warm" path
>    KVM: VMX: Use x2apic_mode to avoid RDMSR when querying PI state
> 
>   arch/x86/kernel/apic/apic.c    | 1 +
>   arch/x86/kvm/vmx/posted_intr.c | 6 +++---
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 

Queued, thanks.

Paolo