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

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Message-ID: <7060AA92-0ACD-40F6-868A-5A7234F46C55@amazon.de>
Date:   Tue, 5 Nov 2019 07:05:57 +0000
From:   "Graf (AWS), Alexander" <graf@...zon.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "rkagan@...tuozzo.com" <rkagan@...tuozzo.com>,
        "Schoenherr, Jan H." <jschoenh@...zon.de>,
        "Raslan, KarimAllah" <karahmed@...zon.de>,
        "Lukaszewicz, Rimas" <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.



> Am 04.11.2019 um 22:50 schrieb Paolo Bonzini <pbonzini@...hat.com>:
> 
> 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.

I'm trying to wrap my head around how that will work with live migration. Do we also need to save/restore the deactivate reasons?

Alex

> 
> Paolo



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