[PATCH 0/3] idle, Honor Hardware Disabled States

[Prarit Bhargava]

Some Intel processors have cstates limited by MSR_PKG_CST_CONFIG_CONTROL
(0xE2), which specifies the lowest processor-specific C-state code name
(consuming the least power).  The intel_idle driver does not query this MSR to
see if states are limited by hardware.  In the case of the i7-6700HQ the value
of bits 3:0 on the MSR are 0x6, meaning that C9-SKL (0x7) and C10-SKL (0x8)
should have been disabled.

This patch adds a limit field to the cpuidle_state struct to hold the
cstate encodings for each processor, and queries the values the values
to confirm support.

After applying this patchset the system now boots and reports that
some states have been disabled:

[root@dhcp40-125 ~]# dmesg | grep intel_idle
[    1.163367] intel_idle: MWAIT substates: 0x11142120
[    1.163368] intel_idle: v0.4 model 0x5E
[    1.163369] intel_idle: lapic_timer_reliable_states 0xffffffff
[    1.163370] intel_idle: state C9-SKL (0x7) is disabled.  Max Package limit is 0x6.
[    1.163371] intel_idle: state C10-SKL (0x8) is disabled.  Max Package limit is 0x6.

Cc: x86@xxxxxxxxxx
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Dasaratharaman Chandramouli <dasaratharaman.chandramouli@xxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>

Prarit Bhargava (3):
  idle, rename MSR_NHM_SNB_PKG_CST_CFG_CTL to
    MSR_PKG_CST_CONFIG_CONTROL
  intel_idle, Introduce cstate limits and fix hardware cstate disable
    value
  cpuidle, Prevent users from enabling cstates that are disabled in
    Hardware

 arch/x86/include/asm/msr-index.h      |    2 +-
 drivers/cpuidle/governors/ladder.c    |    3 ++
 drivers/cpuidle/governors/menu.c      |    4 ++
 drivers/cpuidle/sysfs.c               |   34 +++++++++++-
 drivers/idle/intel_idle.c             |   93 ++++++++++++++++++++++++++++++++-
 include/linux/cpuidle.h               |   11 +++-
 tools/power/x86/turbostat/turbostat.8 |    2 +-
 tools/power/x86/turbostat/turbostat.c |   10 ++--
 8 files changed, 146 insertions(+), 13 deletions(-)

-- 
1.7.9.3