diff options
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/cpu/intel.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 44 |
2 files changed, 33 insertions, 15 deletions
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index fd5dead8371c..663f6e6dd288 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -682,9 +682,9 @@ static void init_intel(struct cpuinfo_x86 *c) unsigned int l1, l2; rdmsr(MSR_IA32_MISC_ENABLE, l1, l2); - if (!(l1 & (1<<11))) + if (!(l1 & MSR_IA32_MISC_ENABLE_BTS_UNAVAIL)) set_cpu_cap(c, X86_FEATURE_BTS); - if (!(l1 & (1<<12))) + if (!(l1 & MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL)) set_cpu_cap(c, X86_FEATURE_PEBS); } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index d456ce21c255..58a6ea472db9 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -810,24 +810,43 @@ static void amd_e400_idle(void) } /* - * Intel Core2 and older machines prefer MWAIT over HALT for C1. - * We can't rely on cpuidle installing MWAIT, because it will not load - * on systems that support only C1 -- so the boot default must be MWAIT. + * Prefer MWAIT over HALT if MWAIT is supported, MWAIT_CPUID leaf + * exists and whenever MONITOR/MWAIT extensions are present there is at + * least one C1 substate. * - * Some AMD machines are the opposite, they depend on using HALT. - * - * So for default C1, which is used during boot until cpuidle loads, - * use MWAIT-C1 on Intel HW that has it, else use HALT. + * Do not prefer MWAIT if MONITOR instruction has a bug or idle=nomwait + * is passed to kernel commandline parameter. */ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) { - if (c->x86_vendor != X86_VENDOR_INTEL) + u32 eax, ebx, ecx, edx; + + /* User has disallowed the use of MWAIT. Fallback to HALT */ + if (boot_option_idle_override == IDLE_NOMWAIT) return 0; - if (!cpu_has(c, X86_FEATURE_MWAIT) || boot_cpu_has_bug(X86_BUG_MONITOR)) + /* MWAIT is not supported on this platform. Fallback to HALT */ + if (!cpu_has(c, X86_FEATURE_MWAIT)) return 0; - return 1; + /* Monitor has a bug. Fallback to HALT */ + if (boot_cpu_has_bug(X86_BUG_MONITOR)) + return 0; + + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); + + /* + * If MWAIT extensions are not available, it is safe to use MWAIT + * with EAX=0, ECX=0. + */ + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) + return 1; + + /* + * If MWAIT extensions are available, there should be at least one + * MWAIT C1 substate present. + */ + return (edx & MWAIT_C1_SUBSTATE_MASK); } /* @@ -932,9 +951,8 @@ static int __init idle_setup(char *str) } else if (!strcmp(str, "nomwait")) { /* * If the boot option of "idle=nomwait" is added, - * it means that mwait will be disabled for CPU C2/C3 - * states. In such case it won't touch the variable - * of boot_option_idle_override. + * it means that mwait will be disabled for CPU C1/C2/C3 + * states. */ boot_option_idle_override = IDLE_NOMWAIT; } else |