From abe48b108247e9b90b4c6739662a2e5c765ed114 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Thu, 14 Jul 2011 00:53:24 -0400 Subject: x86, intel, power: Initialize MSR_IA32_ENERGY_PERF_BIAS 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 Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1107140051020.18606@x980 Acked-by: Rafael J. Wysocki Signed-off-by: H. Peter Anvin Cc: --- arch/x86/kernel/cpu/intel.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'arch/x86/kernel/cpu/intel.c') diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 1edf5ba4fb2..da0d779ecd9 100644 --- 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 -- cgit v1.2.3-70-g09d2 From 17edf2d79f1ea6dfdb4c444801d928953b9f98d6 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 15 Jul 2011 17:37:15 -0400 Subject: x86, intel, power: Correct the MSR_IA32_ENERGY_PERF_BIAS message Fix the printk_once() so that it actually prints (didn't print before due to a stray comma.) [ hpa: changed to an incremental patch and adjusted the description accordingly. ] Signed-off-by: Len Brown Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1107151732480.18606@x980 Cc: Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/intel.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'arch/x86/kernel/cpu/intel.c') diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index da0d779ecd9..ed6086eedf1 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -465,11 +465,11 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c) 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"); + if ((epb & 0xF) == ENERGY_PERF_BIAS_PERFORMANCE) { + printk_once(KERN_WARNING "ENERGY_PERF_BIAS:" + " Set to 'normal', was 'performance'\n" + "ENERGY_PERF_BIAS: View and update with" + " x86_energy_perf_policy(8)\n"); epb = (epb & ~0xF) | ENERGY_PERF_BIAS_NORMAL; wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb); } -- cgit v1.2.3-70-g09d2