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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-03-21 23:20:17 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-04-07 22:33:42 +0200
commitb9c273babce791cf228fc466577f55056a699f9c (patch)
treeea9f1103024da00c2ee7804984cac36366cd43bc /Documentation/ABI
parent5861381d486601430cccf64849bd0a226154bc0d (diff)
PM / arch: x86: MSR_IA32_ENERGY_PERF_BIAS sysfs interface
The Performance and Energy Bias Hint (EPB) is expected to be set by user space through the generic MSR interface, but that interface is not particularly nice and there are security concerns regarding it, so it is not always available. For this reason, add a sysfs interface for reading and updating the EPB, in the form of a new attribute, energy_perf_bias, located under /sys/devices/system/cpu/cpu#/power/ for online CPUs that support the EPB feature. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Acked-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu18
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 9605dbd4b5b5..7f4af7da3fbc 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -518,3 +518,21 @@ Description: Control Symetric Multi Threading (SMT)
If control status is "forceoff" or "notsupported" writes
are rejected.
+
+What: /sys/devices/system/cpu/cpu#/power/energy_perf_bias
+Date: March 2019
+Contact: linux-pm@vger.kernel.org
+Description: Intel Energy and Performance Bias Hint (EPB)
+
+ EPB for the given CPU in a sliding scale 0 - 15, where a value
+ of 0 corresponds to a hint preference for highest performance
+ and a value of 15 corresponds to the maximum energy savings.
+
+ In order to change the EPB value for the CPU, write either
+ a number in the 0 - 15 sliding scale above, or one of the
+ strings: "performance", "balance-performance", "normal",
+ "balance-power", "power" (that represent values reflected by
+ their meaning), to this attribute.
+
+ This attribute is present for all online CPUs supporting the
+ Intel EPB feature.