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x86: use cpuid to check MWAIT support for C1

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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>
This commit is contained in:
Thomas Gleixner 2008-06-09 18:04:27 +02:00 committed by Ingo Molnar
parent 732d7be17b
commit 09fd4b4ef5
1 changed files with 20 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

28
arch/x86/kernel/process.c
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@ -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)