Messages in this thread | | | From | "Yu, Fenghua" <> | Date | Wed, 3 Aug 2011 09:34:46 -0700 | Subject | RE: [PATCH 1/2] x86: Enable fast strings on Intel if BIOS hasn't already |
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> -----Original Message----- > From: Andy Lutomirski [mailto:luto@MIT.EDU] > Sent: Wednesday, August 03, 2011 8:47 AM > To: x86@kernel.org; linux-kernel@vger.kernel.org > Cc: Yu, Fenghua; Andy Lutomirski > Subject: [PATCH 1/2] x86: Enable fast strings on Intel if BIOS hasn't > already > > I have two Sandy Bridge systems and neither one enables fast strings > in BIOS. I can't find anything in the manual that says that only > BIOS should enable or disable the feature, so try to enable it at > bootup. > > Signed-off-by: Andy Lutomirski <luto@mit.edu> > --- > arch/x86/kernel/cpu/intel.c | 17 +++++++++++++++-- > 1 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index ed6086e..6b20fef 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)) { > @@ -118,10 +119,11 @@ 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; > + printk(KERN_INFO "kmemcheck: Disabling fast string > operations\n");
Please don't move this printk() here. Keep it in the original place. If fast string bit is 0 already, we don't need to print the info.
> > + 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"); > > misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; > wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); > @@ -135,6 +137,17 @@ static void __cpuinit early_init_intel(struct > cpuinfo_x86 *c)
You also need to change the comment right before this code. With your patch, the comment is out-of-date.
> */ > 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; > + wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); > + printk(KERN_INFO "Enabled fast string operations\n"); > + > + /* 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_INFO "Disabled fast string > operations\n"); > setup_clear_cpu_cap(X86_FEATURE_REP_GOOD); > -- > 1.7.6
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