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 ealier patch from Andi Kleen. Signed-off-by: Thomas Gleixner Cc: Andreas Herrmann --- arch/x86/kernel/process.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) Index: linux-2.6/arch/x86/kernel/process.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/process.c +++ linux-2.6/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 enumerates MONITOR/MWAIT extensions. Check, whether C1 + * supports MWAIT + */ + return edx & MWAIT_EDX_C1; } void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/