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

["H. Peter Anvin" <hpa@zytor.com>]

On 05/11/2011 03:36 PM, Andi Kleen wrote:
> "Fenghua Yu"<fenghua.yu@intel.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

SMEP only matters if we can into userspace code, so I *think* the above 
should be okay.  However, the most logical place would be to enable it 
in the same place(s) where we enable NX.

	-hpa