Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH 1/2] x86: Enable fast strings on Intel if BIOS hasn't already | Date | Wed, 3 Aug 2011 11:47:16 -0400 |
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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"); + 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) */ 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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