ACPI : Create "idle=nomwait" bootparam
"idle=nomwait" disables the use of the MWAIT
instruction from both C1 (C1_FFH) and deeper (C2C3_FFH)
C-states.
When MWAIT is unavailable, the BIOS and OS generally
negotiate to use the HALT instruction for C1,
and use IO accesses for deeper C-states.
This option is useful for power and performance
comparisons, and also to work around BIOS bugs
where broken MWAIT support is advertised.
http://bugzilla.kernel.org/show_bug.cgi?id=10807
http://bugzilla.kernel.org/show_bug.cgi?id=10914
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 65db7f4..5e497d1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -818,7 +818,7 @@
See Documentation/ide/ide.txt.
idle= [X86]
- Format: idle=poll or idle=mwait, idle=halt
+ Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
Poll forces a polling idle loop that can slightly improves the performance
of waking up a idle CPU, but will use a lot of power and make the system
run hot. Not recommended.
@@ -828,6 +828,7 @@
as idle=poll.
idle=halt. Halt is forced to be used for CPU idle.
In such case C2/C3 won't be used again.
+ idle=nomwait. Disable mwait for CPU C-states
ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
Claim all unknown PCI IDE storage controllers.
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 612b3c4..3ab8373 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -57,6 +57,8 @@
EXPORT_SYMBOL(boot_option_idle_override);
unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt);
+unsigned long idle_nomwait;
+EXPORT_SYMBOL(idle_nomwait);
void
ia64_do_show_stack (struct unw_frame_info *info, void *arg)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 7fc7294..4d629c6 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -11,6 +11,8 @@
unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt);
+unsigned long idle_nomwait;
+EXPORT_SYMBOL(idle_nomwait);
struct kmem_cache *task_xstate_cachep;
@@ -340,6 +342,15 @@
pm_idle = default_idle;
idle_halt = 1;
return 0;
+ } 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.
+ */
+ idle_nomwait = 1;
+ return 0;
} else
return -1;
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 9a803f8..4e1bb89 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -265,7 +265,20 @@
if (!pdc_in)
return status;
+ if (idle_nomwait) {
+ /*
+ * If mwait is disabled for CPU C-states, the C2C3_FFH access
+ * mode will be disabled in the parameter of _PDC object.
+ * Of course C1_FFH access mode will also be disabled.
+ */
+ union acpi_object *obj;
+ u32 *buffer = NULL;
+ obj = pdc_in->pointer;
+ buffer = (u32 *)(obj->buffer.pointer);
+ buffer[2] &= ~(ACPI_PDC_C_C2C3_FFH | ACPI_PDC_C_C1_FFH);
+
+ }
status = acpi_evaluate_object(pr->handle, "_PDC", pdc_in, NULL);
if (ACPI_FAILURE(status))
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index c75c7ac..d592dbb 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -957,13 +957,17 @@
} else {
continue;
}
- if (cx.type == ACPI_STATE_C1 && idle_halt) {
+ if (cx.type == ACPI_STATE_C1 &&
+ (idle_halt || idle_nomwait)) {
/*
* In most cases the C1 space_id obtained from
* _CST object is FIXED_HARDWARE access mode.
* But when the option of idle=halt is added,
* the entry_method type should be changed from
* CSTATE_FFH to CSTATE_HALT.
+ * When the option of idle=nomwait is added,
+ * the C1 entry_method type should be
+ * CSTATE_HALT.
*/
cx.entry_method = ACPI_CSTATE_HALT;
snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index f36e28a..f88fa05 100644
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -764,6 +764,7 @@
extern unsigned long boot_option_idle_override;
extern unsigned long idle_halt;
+extern unsigned long idle_nomwait;
#endif /* !__ASSEMBLY__ */
diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index bc22162..55402d2 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -728,6 +728,7 @@
extern unsigned long boot_option_idle_override;
extern unsigned long idle_halt;
+extern unsigned long idle_nomwait;
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);