linux-kernel - Re: [PATCH 3/3] x86, cpu: Enable/disable SMEP

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Date:	Wed, 11 May 2011 15:36:30 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	"Fenghua Yu" <fenghua.yu@...el.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H Peter Anvin" <hpa@...or.com>,
	"Asit K Mallick" <asit.k.mallick@...el.com>,
	"linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86, cpu: Enable/disable SMEP

"Fenghua Yu" <fenghua.yu@...el.com> writes:
  
> +static int disable_smep;

If you add a __initdata here the whole thing will completely disappear
after boot.

> @@ -867,6 +886,8 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
>  	/* Init Machine Check Exception if available. */
>  	mcheck_cpu_init(c);
>  
> +	setup_smep(c);

My feeling is you're setting this too late. In theory there could be
early overflows. Better use a early_param and set it as early
as possible, directly after the cpuid flags are set up in early
initialization.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only
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