From 161ec53c702ce9df2f439804dfb9331807066daa Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Tue, 17 May 2011 15:29:11 -0700 Subject: [PATCH] x86, mem, intel: Initialize Enhanced REP MOVSB/STOSB If kernel intends to use enhanced REP MOVSB/STOSB, it must ensure IA32_MISC_ENABLE.Fast_String_Enable (bit 0) is set and CPUID.(EAX=07H, ECX=0H): EBX[bit 9] also reports 1. Signed-off-by: Fenghua Yu Link: http://lkml.kernel.org/r/1305671358-14478-3-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/intel.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index df86bc8..fc73a34 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -29,10 +29,10 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) { + u64 misc_enable; + /* Unmask CPUID levels if masked: */ if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) { - u64 misc_enable; - rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); if (misc_enable & MSR_IA32_MISC_ENABLE_LIMIT_CPUID) { @@ -118,8 +118,6 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) * (model 2) with the same problem. */ if (c->x86 == 15) { - u64 misc_enable; - rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); if (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING) { @@ -130,6 +128,19 @@ 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 (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) { + 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); + setup_clear_cpu_cap(X86_FEATURE_ERMS); + } + } } #ifdef CONFIG_X86_32 -- 2.7.4