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

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Message-ID: <493994B35A117E4F832F97C4719C4C040132CE88A0@orsmsx505.amr.corp.intel.com>
Date:	Wed, 10 Aug 2011 08:05:38 -0700
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Andrew Lutomirski <luto@....edu>
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

> -----Original Message-----
> From: amluto@...il.com [mailto:amluto@...il.com] On Behalf Of Andrew
> Lutomirski
> Sent: Wednesday, August 10, 2011 7:50 AM
> To: Yu, Fenghua
> Cc: x86@...nel.org; linux-kernel@...r.kernel.org; Matthew Garrett; Len
> Brown; linux-acpi@...r.kernel.org; Ingo Molnar; Anvin, H Peter
> 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.

+				printk_once(KERN_INFO FW_WARN "CPU #%d: IA32_MISC_ENABLE.FAST_STRING_ENABLE was not set",
There is no need to print CPU id. Then there is no SMP issue.

Thanks.

-Fenghua


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