From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753306Ab1HIPNE (ORCPT ); Tue, 9 Aug 2011 11:13:04 -0400 Received: from mail-gw0-f46.google.com ([74.125.83.46]:41784 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753240Ab1HIPNB convert rfc822-to-8bit (ORCPT ); Tue, 9 Aug 2011 11:13:01 -0400 MIME-Version: 1.0 In-Reply-To: <20110809150035.GE28228@elte.hu> References: <9a8f28ccbe44cd323a01e9a23b531cb869185a21.1312630712.git.luto@mit.edu> <493994B35A117E4F832F97C4719C4C040132C5FB69@orsmsx505.amr.corp.intel.com> <493994B35A117E4F832F97C4719C4C040132C5FBE0@orsmsx505.amr.corp.intel.com> <20110809150035.GE28228@elte.hu> From: Andrew Lutomirski Date: Tue, 9 Aug 2011 11:12:38 -0400 X-Google-Sender-Auth: K-MGHHAPTlXt2C_US4EXKLUibq0 Message-ID: Subject: Re: [PATCH v2 1/2] x86: Enable fast strings on Intel if BIOS hasn't already To: Ingo Molnar Cc: "Yu, Fenghua" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Matthew Garrett , Len Brown , "linux-acpi@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 9, 2011 at 11:00 AM, Ingo Molnar wrote: > > * Yu, Fenghua wrote: > >> > -----Original Message----- >> > From: amluto@gmail.com [mailto:amluto@gmail.com] On Behalf Of Andrew >> > Lutomirski >> > Sent: Saturday, August 06, 2011 4:32 PM >> > To: Yu, Fenghua >> > Cc: x86@kernel.org; linux-kernel@vger.kernel.org; Matthew Garrett; Len >> > Brown; linux-acpi@vger.kernel.org; Ingo Molnar >> > Subject: Re: [PATCH v2 1/2] x86: Enable fast strings on Intel if BIOS >> > hasn't already >> > >> > On Sat, Aug 6, 2011 at 3:33 PM, Yu, Fenghua >> > wrote: >> > >> -----Original Message----- >> > >> From: Andy Lutomirski [mailto:luto@MIT.EDU] >> > >> Sent: Saturday, August 06, 2011 4:43 AM >> > >> To: x86@kernel.org; linux-kernel@vger.kernel.org >> > >> Cc: Yu, Fenghua; Matthew Garrett; Len Brown; linux- >> > >> acpi@vger.kernel.org; Ingo Molnar; Andy Lutomirski >> > >> Subject: [PATCH v2 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 >> > >> --- >> > >>  arch/x86/kernel/cpu/intel.c |   25 ++++++++++++++++++++++--- >> > >>  1 files changed, 22 insertions(+), 3 deletions(-) >> > >> >> > >> diff --git a/arch/x86/kernel/cpu/intel.c >> > b/arch/x86/kernel/cpu/intel.c >> > >> index ed6086e..c80ab41 100644 >> > >> --- a/arch/x86/kernel/cpu/intel.c >> > >> +++ b/arch/x86/kernel/cpu/intel.c >> > >> @@ -30,6 +30,7 @@ >> > >>  static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) >> > >>  { >> > >>       u64 misc_enable; >> > >> +     bool allow_fast_string = true; >> > >> >> > >>       /* Unmask CPUID levels if masked: */ >> > >>       if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) { >> > >> @@ -118,8 +119,9 @@ static void __cpuinit early_init_intel(struct >> > >> cpuinfo_x86 *c) >> > >>        * (model 2) with the same problem. >> > >>        */ >> > >>       if (c->x86 == 15) { >> > >> -             rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); >> > >> +             allow_fast_string = false; >> > >> >> > >> +             rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); >> > >>               if (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING) { >> > >>                       printk(KERN_INFO "kmemcheck: Disabling fast >> > string >> > >> operations\n"); >> > >> >> > >> @@ -130,11 +132,28 @@ static void __cpuinit early_init_intel(struct >> > >> cpuinfo_x86 *c) >> > >>  #endif >> > >> >> > >>       /* >> > >> -      * If fast string is not enabled in IA32_MISC_ENABLE for any >> > >> reason, >> > >> -      * clear the fast string and enhanced fast string CPU >> > >> capabilities. >> > >> +      * If BIOS didn't enable fast string operation, try to enable >> > >> +      * it ourselves.  If that fails, then clear the fast string >> > >> +      * and enhanced fast string CPU capabilities. >> > >>        */ >> > >>       if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) { >> > >>               rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); >> > >> + >> > >> +             if (allow_fast_string && >> > >> +                 !(misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING)) >> > { >> > >> +                     misc_enable |= >> > MSR_IA32_MISC_ENABLE_FAST_STRING; >> > >> +                     wrmsr_safe(MSR_IA32_MISC_ENABLE, >> > (u32)misc_enable, >> > >> +                                (u32)(misc_enable >> 32)); >> > >> + >> > >> +                     /* Re-read to make sure it stuck. */ >> > >> +                     rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); >> > >> + >> > >> +                     if (misc_enable & >> > MSR_IA32_MISC_ENABLE_FAST_STRING) >> > >> +                             printk(KERN_WARNING FW_WARN "CPU #%d: >> > " >> > >> + >> >  "IA32_MISC_ENABLE.FAST_STRING_ENABLE " >> > >> +                                    "was not set", c->cpu_index); >> > > This printk is redundant because the same info is dumped in the below >> > printk. Plus it's not firmware's issue if we can not set fast string >> > bit 0 in MISC_ENABLE register. So I don't think FW_WARN is right. >> > >> > Huh?  This is the success path -- the patch prints the warning if >> > flipping the bit worked... >> >> Ok. I see. >> >> Still I would suggest to remove this printk. This info will be >> printed on every single CPU if BIOS doesn't enable fast string. > > just do printk_once(). We want to inform the user that something's > going on. Already there in v3. --Andy > > Thanks, > >        Ingo >