linux-kernel - Re: [PATCH] x86/cpufeature: Add AMD AVIC bit

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Date:	Tue, 19 Jan 2016 13:39:00 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	David Kaplan <david.kaplan@....com>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH] x86/cpufeature: Add AMD AVIC bit

On Sat, Jan 16, 2016 at 10:58:12AM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> CPUID Fn8000_000A_EDX[13] denotes support for AMD's Virtual Interrupt
> controller, i.e., APIC virtualization.
> 
> Cc: David Kaplan <david.kaplan@....com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
>  arch/x86/include/asm/cpufeature.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 7ad8c9464297..bbf166e805be 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -268,6 +268,7 @@
>  #define X86_FEATURE_DECODEASSISTS (15*32+ 7) /* Decode Assists support */
>  #define X86_FEATURE_PAUSEFILTER (15*32+10) /* filtered pause intercept */
>  #define X86_FEATURE_PFTHRESHOLD (15*32+12) /* pause filter threshold */
> +#define X86_FEATURE_AVIC	(15*32+13) /* Virtual Interrupt Controller */

That is not enough, you also need to add the feature to the scattered
cpuid_bits in arch/x86/kernel/cpu/scattered.c.
The cpuid Fn8000_000A_EDX is not mapped 1-1 into the x86_capability
array.


	Joerg