From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Asit K Mallick <asit.k.mallick@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] x86, cpu: Enable/disable SMEP
Date: Wed, 11 May 2011 23:06:37 -0700 [thread overview]
Message-ID: <4DCB78ED.9040409@zytor.com> (raw)
In-Reply-To: <m2k4dwj24x.fsf@firstfloor.org>
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
next prev parent reply other threads:[~2011-05-12 6:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-11 19:17 [PATCH 0/3] Enable SMEP CPU Feature Fenghua Yu
2011-05-11 19:17 ` [PATCH 1/3] x86, cpu: Add CPU flags for SMEP Fenghua Yu
2011-05-11 19:17 ` [PATCH 2/3] x86, cpu: Add SMEP CPU feature in CR4 Fenghua Yu
2011-05-11 19:18 ` [PATCH 3/3] x86, cpu: Enable/disable SMEP Fenghua Yu
2011-05-11 22:36 ` Andi Kleen
2011-05-12 6:06 ` H. Peter Anvin [this message]
2011-05-12 6:59 ` Ingo Molnar
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