diff options
| -rw-r--r-- | arch/x86/kernel/process_32.c | 29 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 29 |
2 files changed, 56 insertions, 2 deletions
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 54bb813bc29b..39b1b7e76a5b 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -259,6 +259,33 @@ static void mwait_idle(void) mwait_idle_with_hints(0, 0); } +/* + * mwait selection logic: + * + * It depends on the CPU. For AMD CPUs that support MWAIT this is + * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings + * then depend on a clock divisor and current Pstate of the core. If + * all cores of a processor are in halt state (C1) the processor can + * enter the C1E (C1 enhanced) state. If mwait is used this will never + * happen. + * + * idle=mwait overrides this decision and forces the usage of mwait. + */ +static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) +{ + if (force_mwait) + return 1; + + if (c->x86_vendor == X86_VENDOR_AMD) { + switch(c->x86) { + case 0x10: + case 0x11: + return 0; + } + } + return 1; +} + void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) { static int selected; @@ -271,7 +298,7 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) " performance may degrade.\n"); } #endif - if (cpu_has(c, X86_FEATURE_MWAIT)) { + if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) { /* * Skip, if setup has overridden idle. * One CPU supports mwait => All CPUs supports mwait diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index fbb171fc2bee..53b9c4c0572e 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -254,6 +254,33 @@ static void mwait_idle(void) } } +/* + * mwait selection logic: + * + * It depends on the CPU. For AMD CPUs that support MWAIT this is + * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings + * then depend on a clock divisor and current Pstate of the core. If + * all cores of a processor are in halt state (C1) the processor can + * enter the C1E (C1 enhanced) state. If mwait is used this will never + * happen. + * + * idle=mwait overrides this decision and forces the usage of mwait. + */ +static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) +{ + if (force_mwait) + return 1; + + if (c->x86_vendor == X86_VENDOR_AMD) { + switch(c->x86) { + case 0x10: + case 0x11: + return 0; + } + } + return 1; +} + void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) { static int selected; @@ -266,7 +293,7 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) " performance may degrade.\n"); } #endif - if (cpu_has(c, X86_FEATURE_MWAIT)) { + if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) { /* * Skip, if setup has overridden idle. * One CPU supports mwait => All CPUs supports mwait |