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Subject[tip:perf/core] x86, mem, intel: Initialize Enhanced REP MOVSB/STOSB
Commit-ID:  161ec53c702ce9df2f439804dfb9331807066daa
Gitweb: http://git.kernel.org/tip/161ec53c702ce9df2f439804dfb9331807066daa
Author: Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Tue, 17 May 2011 15:29:11 -0700
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Tue, 17 May 2011 15:40:23 -0700

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 <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1305671358-14478-3-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/kernel/cpu/intel.c | 19 +++++++++++++++----
1 files 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

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