linux-kernel - Re: [PATCH 24/32] x86, pkeys: actually enable Memory Protection Keys in CPU

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Date:	Mon, 14 Dec 2015 21:00:52 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave@...1.net>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 24/32] x86, pkeys: actually enable Memory Protection Keys
 in CPU

On Mon, 14 Dec 2015, Dave Hansen wrote:
> This sets the bit in 'cr4' to actually enable the protection
> keys feature.  We also include a boot-time disable for the
> feature "nopku".
> 
> Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE cpuid
> bit to appear set.  At this point in boot, identify_cpu()
> has already run the actual CPUID instructions and populated
> the "cpu features" structures.  We need to go back and
> re-run identify_cpu() to make sure it gets updated values.
> 
> We *could* simply re-populate the 11th word of the cpuid
> data, but this is probably quick enough.
> 
> Also note that with the cpu_has() check and X86_FEATURE_PKU
> present in disabled-features.h, we do not need an #ifdef
> for setup_pku().
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
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