x86, intel, power: Initialize MSR_IA32_ENERGY_PERF_BIAS

commit abe48b108247e9b90b4c6739662a2e5c765ed114 upstream.

Since 2.6.36 (23016bf0d25), Linux prints the existence of "epb" in /proc/cpuinfo,
Since 2.6.38 (d5532ee7b40), the x86_energy_perf_policy(8) utility has
been available in-tree to update MSR_IA32_ENERGY_PERF_BIAS.

However, the typical BIOS fails to initialize the MSR, presumably
because this is handled by high-volume shrink-wrap operating systems...

Linux distros, on the other hand, do not yet invoke x86_energy_perf_policy(8).
As a result, WSM-EP, SNB, and later hardware from Intel will run in its
default hardware power-on state (performance), which assumes that users
care for performance at all costs and not for energy efficiency.
While that is fine for performance benchmarks, the hardware's intended default
operating point is "normal" mode...

Initialize the MSR to the "normal" by default during kernel boot.

x86_energy_perf_policy(8) is available to change the default after boot,
should the user have a different preference.

Signed-off-by: Len Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1107140051020.18606@x980
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 485b4f1f079b130346c584d78e5a5edbd47d3267..23a9d898baad8322b9fa33f63e81f4aad7316ff3 100644 (file)
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -259,6 +259,9 @@
 #define MSR_IA32_TEMPERATURE_TARGET    0x000001a2
 
 #define MSR_IA32_ENERGY_PERF_BIAS      0x000001b0
+#define ENERGY_PERF_BIAS_PERFORMANCE   0
+#define ENERGY_PERF_BIAS_NORMAL                6
+#define ENERGY_PERF_BIAS_POWERSWAVE    15
 
 #define MSR_IA32_PACKAGE_THERM_STATUS          0x000001b1
 

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 1edf5ba4fb2b76076f448db70d01587c71a96d3d..da0d779ecd9ecc3be2d8fb8d7284210a6e704456 100644 (file)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -456,6 +456,24 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
 
        if (cpu_has(c, X86_FEATURE_VMX))
                detect_vmx_virtcap(c);
+
+       /*
+        * Initialize MSR_IA32_ENERGY_PERF_BIAS if BIOS did not.
+        * x86_energy_perf_policy(8) is available to change it at run-time
+        */
+       if (cpu_has(c, X86_FEATURE_EPB)) {
+               u64 epb;
+
+               rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
+               if ((epb & 0xF) == 0) {
+                       printk_once(KERN_WARNING, "x86: updated energy_perf_bias"
+                               " to 'normal' from 'performance'\n"
+                               "You can view and update epb via utility,"
+                               " such as x86_energy_perf_policy(8)\n");
+                       epb = (epb & ~0xF) | ENERGY_PERF_BIAS_NORMAL;
+                       wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
+               }
+       }
 }
 
 #ifdef CONFIG_X86_32