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>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index f36e28a5f61e..f88fa054d01d 100644
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -764,6 +764,7 @@ prefetchw (const void *x)
 
 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 bc221623248e..55402d2ab938 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -728,6 +728,7 @@ extern void select_idle_routine(const struct cpuinfo_x86 *c);
 
 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);