linux-kernel - Re: [PATCH v3 1/2] x86: Enable fast strings on Intel if BIOS hasn't already

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Message-ID: <CAObL_7EozFSbcqJiwV=PNH-3sN0M1QfaTu3i4A_OKsZ0Ue5g7A@mail.gmail.com>
Date:	Wed, 10 Aug 2011 10:49:38 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
Cc:	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Len Brown <lenb@...nel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Anvin, H Peter" <h.peter.anvin@...el.com>
Subject: Re: [PATCH v3 1/2] x86: Enable fast strings on Intel if BIOS hasn't already

On Tue, Aug 9, 2011 at 11:40 AM, Yu, Fenghua <fenghua.yu@...el.com> wrote:
>> -----Original Message-----
>> From: Andy Lutomirski [mailto:luto@....EDU]
>> Sent: Tuesday, August 09, 2011 5:41 AM
>> To: x86@...nel.org; linux-kernel@...r.kernel.org
>> Cc: Yu, Fenghua; Matthew Garrett; Len Brown; linux-
>> acpi@...r.kernel.org; Ingo Molnar; Andy Lutomirski
>> Subject: [PATCH v3 1/2] x86: Enable fast strings on Intel if BIOS
>> hasn't already
>>
>> Intel SDM volume 3A, 8.4.2 says:
>>
>>   Software can disable fast-string operation by clearing the
>>   fast-string-enable bit (bit 0) of IA32_MISC_ENABLE MSR.
>>   However, Intel recomments that system software always enable
>>   fast-string operation.
>>
>> The Intel DQ67SW board (with latest BIOS) disables fast string
>> operations if TXT is enabled.  A Lenovo X220 disables it regardless
>> of TXT setting.  I doubt I'm the only person with a dumb BIOS like
>> this.
>>
>> Signed-off-by: Andy Lutomirski <luto@....edu>
>> ---
>>  arch/x86/kernel/cpu/intel.c |   28 +++++++++++++++++++++++-----
>>  1 files changed, 23 insertions(+), 5 deletions(-)
>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
>
>

Please don't apply.  This patch breaks !CONFIG_SMP.  I'll send a fixed
patch later on.

--Andy
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