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authorThomas Gleixner <tglx@linutronix.de>2008-06-19 16:34:26 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2008-06-21 22:24:57 -0700
commitf8bd72872adbf6cc36f370f5c6319085c3be3ec3 (patch)
treec1dffefa9de5fba91a15174f3063704219a072de
parent384353364373c7c9f8134a847a35e27642cb6dae (diff)
x86: disable mwait for AMD family 10H/11H CPUs
back-ported from upstream commit e9623b35599fcdbc00c16535cbefbb4d5578f4ab by Vegard Nossum The previous revert of 0c07ee38c9d4eb081758f5ad14bbffa7197e1aec left out the mwait disable condition for AMD family 10H/11H CPUs. Andreas Herrman said: 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. Thus HLT saves more power than MWAIT here. It might be best to switch off the mwait flag for these AMD CPU families like it was introduced with commit f039b754714a422959027cb18bb33760eb8153f0 (x86: Don't use MWAIT on AMD Family 10) Re-add the AMD families 10H/11H check and disable the mwait usage for those. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--arch/x86/kernel/process_32.c29
-rw-r--r--arch/x86/kernel/process_64.c29
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