linux-kernel - Re: [PART1 V5 08/13] svm: Add interrupt injection via AVIC

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Date:	Tue, 31 May 2016 23:02:22 -0500
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Paolo Bonzini <pbonzini@...hat.com>, Borislav Petkov <bp@...en8.de>
CC:	<rkrcmar@...hat.com>, <joro@...tes.org>, <gleb@...nel.org>,
	<alex.williamson@...hat.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <wei@...hat.com>,
	<sherry.hurwitz@....com>
Subject: Re: [PART1 V5 08/13] svm: Add interrupt injection via AVIC

Hi,

Sorry for late response on this.

On 5/10/16 09:50, Paolo Bonzini wrote:
>
>
> On 10/05/2016 11:19, Borislav Petkov wrote:
>>>> This patch introduces a new mechanism to inject interrupt using AVIC.
>>>> Since VINTR is not supported when enable AVIC, we need to inject
>> 	"... is not supported when AVIC is enabled ..."
>>
>> VINTR?
>
> The ability to request a vmexit as soon as an interrupt can be injected
> (IF=GIF=1, no interrupt window, etc.).  It's called the "VINTR intercept".
>
>> Please write those things out in the commit message for maximum
>> information transfer to the reader. :)
>
> More important, where does the APM document that VINTR is not supported
> when AVIC is enabled?  It is certainly pointless and inefficient, but
> I'm not sure where it says that it doesn't work.
>
> Paolo
>

Basically, from the APM vol2 here:

   http://developer.amd.com/wordpress/media/2012/10/24593_APM_v21.pdf

On page 115, section AVIC Enable—Virtual Interrupt Control, Bit 31:

   "... Enabling AVIC implicitly disables the V_IRQ, V_INTR_PRIO,
    V_IGN_TPR, and V_INTR_VECTOR fields in the VMCB Control Word."

Thanks,
Suravee