linux-kernel - Re: [PATCH] x86, amd: Make check_c1e

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Message-ID: <4B219A6F.1060801@zytor.com>
Date:	Thu, 10 Dec 2009 17:03:43 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andreas Herrmann <herrmann.der.user@...glemail.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH] x86, amd: Make check_c1e_idle explicit

This patch needs a lot better documentation.  For one thing, it needs an
explicit patch comment!

In particular, is this a contract that fam 0x12+ will behave differently?

	-hpa

On 12/10/2009 05:32 AM, Andreas Herrmann wrote:
> 
> CC: stable@...nel.org
> Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
> ---
>  arch/x86/kernel/process.c |   14 ++++++--------
>  1 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index ea54ce8..1bf98b1 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -494,21 +494,19 @@ static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
>  }
>  
>  /*
> - * Check for AMD CPUs, which have potentially C1E support
> + * Check for AMD CPUs, which potentially use SMI or hardware initiated C1E
>   */
>  static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
>  {
>  	if (c->x86_vendor != X86_VENDOR_AMD)
>  		return 0;
>  
> -	if (c->x86 < 0x0F)
> -		return 0;
> -
> -	/* Family 0x0f models < rev F do not have C1E */
> -	if (c->x86 == 0x0f && c->x86_model < 0x40)
> -		return 0;
> +	if ((c->x86 == 0x0F && c->x86_model >= 0x40) ||
> +	    (c->x86 == 0x10) ||
> +	    (c->x86 == 0x11))
> +		return 1;
>  
> -	return 1;
> +	return 0;
>  }
>  
>  static cpumask_var_t c1e_mask;

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