[PATCH v12 0/5] Enabling Ring 3 MONITOR/MWAIT feature for Knights Landing

[Grzegorz Andrejczuk]

Following patches enable the use of the feature that allows
the Intel Xeon Phi x200 devices to use MONITOR/MWAIT instructions
outside ring 0. This feature allows userspace application to use
more efficient synchronization operations, which improves performance
and energy efficiency.

v12:
Removed unused define from msr-info.h
Added braces in define ELF_HWCAP
Set HWCAP2_RING3MWAIT bit only for boot cpu
Replaced set_bit by bit OR operator
Updated ring3mwait_disable return value
Rebased to kernel 4.10rc4
Updated commit messages

v11:
Removed warning from 32-bit build
Removed "This patch" from commit messages

v10:
Included Piotr's patch for Knights Mill
Included Dave's comments from internal review
Rewritten commit messages
Remove x86_64 requirement
Fixed kernel boot parameter description
Used set_bit to update HWCAP2 bit
Rebased to kernel 4.9

v9:
Removed PHI from defines

v8:
Fixed commit messages
Removed logging
Used msr_set/clear_bit functions instesd of wrmsrl
Fixed documentation
Renamed HWCAP2_PHIR3MWAIT to HWCAP2_RING3MWAIT

v7:
Change order of the patches, with this code looks cleaner.
Changed the name of MSR to MSR_MISC_FEATURE_ENABLES.
Used Word 3 25th bit to expose feature.

v6:

v5:
When phir3mwait=disable is cmdline switch off r3 mwait feature
Fix typos

v4:
Wrapped the enabling code by CONFIG_X86_64
Add documentation for phir3mwait=disable cmdline switch
Move probe_ function call from early_intel_init to intel_init
Fixed commit messages

v3:
Included Daves and Thomas comments

v2:
Check MSR before wrmsrl
Shortened names
Used Word 3 for feature init_scattered_cpuid_features()
Fixed commit messages

Grzegorz Andrejczuk (4):
  x86/msr: add MSR_MISC_FEATURE_ENABLES and RING3MWAIT bit
  x86/elf: add HWCAP2 to expose ring 3 MONITOR/MWAIT
  x86/cpufeature: add RING3MWAIT to CPU features
  x86/cpufeature: enable RING3MWAIT for Knights Landing

Piotr Luc (1):
  x86/cpufeature: enable RING3MWAIT for Knights Mill

 Documentation/admin-guide/kernel-parameters.txt |  4 +++
 arch/x86/include/asm/cpufeatures.h              |  2 +-
 arch/x86/include/asm/elf.h                      |  9 ++++++
 arch/x86/include/asm/msr-index.h                |  5 ++++
 arch/x86/include/uapi/asm/hwcap2.h              |  7 +++++
 arch/x86/kernel/cpu/common.c                    |  3 ++
 arch/x86/kernel/cpu/intel.c                     | 39 +++++++++++++++++++++++++
 7 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/include/uapi/asm/hwcap2.h

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2.5.1