linux-kernel - Re: [PATCH v2 3/5] KVM: x86: Use common 'enable

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Message-ID: <5d8b607b-f280-fd3e-c147-94111468d5a1@redhat.com>
Date:   Thu, 27 May 2021 13:39:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Kechen Lu <kechenl@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] KVM: x86: Use common 'enable_apicv' variable for
 both APICv and AVIC

On 26/05/21 17:52, Maxim Levitsky wrote:
>> I don't love the intermediate "avic" either, but there isn't a good alternative.
>> Forcing VMX to also use an intermediate doesn't make much sense, we'd be penalizing
>> ourselves in the form of unnecessary complexity just because AVIC needs to be
>> disabled by default for reasons KVM can't fix.
> This is also something we should eventually reconsider.
> These days, the AVIC works quite well and disables itself when needed.
> When do you think it will be the time to enable it by default?

We can probably enable it, but most guests won't use it because of x2apic.

Paolo