linux-kernel - Re: [PATCH v4 13/17] kvm: i8254: Deactivate APICv when using in-kernel PIT re-injection mode.

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Date:   Mon, 4 Nov 2019 22:49:24 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "rkagan@...tuozzo.com" <rkagan@...tuozzo.com>,
        "graf@...zon.com" <graf@...zon.com>,
        "jschoenh@...zon.de" <jschoenh@...zon.de>,
        "karahmed@...zon.de" <karahmed@...zon.de>,
        "rimasluk@...zon.com" <rimasluk@...zon.com>,
        "Grimm, Jon" <Jon.Grimm@....com>
Subject: Re: [PATCH v4 13/17] kvm: i8254: Deactivate APICv when using
 in-kernel PIT re-injection mode.

On 04/11/19 19:54, Suthikulpanit, Suravee wrote:
> I see you point.
> 
>> We can work around it by adding a global mask of inhibit reasons that
>> apply to the vendor, and initializing it as soon as possible in vmx.c/svm.c.
>>
>> Then kvm_request_apicv_update can ignore reasons that the vendor doesn't
>> care about.
>
> What about we enhance the pre_update_apivc_exec_ctrl() to also return 
> success/fail. In here, the vendor specific code can decide to update 
> APICv state or not.

That works for me, too.  Something like return false for deactivate and
true for activate.

Paolo