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authorThomas Gleixner <tglx@linutronix.de>2008-06-09 18:04:27 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-10 15:52:21 +0200
commit09fd4b4ef5bc7e5222c13acec1bee8cd252fb63f (patch)
treef23eec885a8506c2f84987ac443db618fb58aa27 /arch
parent732d7be17b98ebfd59e5864c3490f19856fa832c (diff)
x86: use cpuid to check MWAIT support for C1
cpuid(0x05) provides extended information about MWAIT in EDX when bit 0 of ECX is set. Bit 4-7 of EDX determine whether MWAIT is supported for C1. C1E enabled CPUs have these bits set to 0. Based on an earlier patch from Andi Kleen. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/process.c28
1 files changed, 20 insertions, 8 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b3078f4ce25..fe415ba606e 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -122,19 +122,31 @@ static void poll_idle(void)
*
* idle=mwait overrides this decision and forces the usage of mwait.
*/
+
+#define MWAIT_INFO 0x05
+#define MWAIT_ECX_EXTENDED_INFO 0x01
+#define MWAIT_EDX_C1 0xf0
+
static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
{
+ u32 eax, ebx, ecx, edx;
+
if (force_mwait)
return 1;
- if (c->x86_vendor == X86_VENDOR_AMD) {
- switch(c->x86) {
- case 0x10:
- case 0x11:
- return 0;
- }
- }
- return 1;
+ if (c->cpuid_level < MWAIT_INFO)
+ return 0;
+
+ cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
+ /* Check, whether EDX has extended info about MWAIT */
+ if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
+ return 1;
+
+ /*
+ * edx enumeratios MONITOR/MWAIT extensions. Check, whether
+ * C1 supports MWAIT
+ */
+ return (edx & MWAIT_EDX_C1);
}
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)