[GIT pull] x86/splitlock for v5.7

[Thomas Gleixner]

Linus,

please pull the latest x86/splitlock branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-splitlock-2020-03-30

up to:  a6a60741035b: x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR

Support for "split lock" detection:

  - Atomic operations (lock prefixed instructions) which span two cache
    lines have to acquire the global bus lock. This is at least 1k cycles
    slower than an atomic operation within a cache line and disrupts
    performance on other cores. Aside of performance disruption this is
    a unpriviledged form of DoS.

    Some newer CPUs have the capability to raise an #AC trap when such an
    operation is attempted. The detection is by default enabled in warning
    mode which will warn once when a user space application is caught. A
    command line option allows to disable the detection or to select fatal
    mode which will terminate offending applications with SIGBUS.

Thanks,

	tglx

------------------>
Peter Zijlstra (Intel) (1):
      x86/split_lock: Enable split lock detection by kernel

Xiaoyao Li (2):
      x86/split_lock: Rework the initialization flow of split lock detection
      x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR


 Documentation/admin-guide/kernel-parameters.txt |  22 +++
 arch/x86/include/asm/cpu.h                      |  12 ++
 arch/x86/include/asm/cpufeatures.h              |   2 +
 arch/x86/include/asm/msr-index.h                |   9 ++
 arch/x86/include/asm/thread_info.h              |   4 +-
 arch/x86/kernel/cpu/common.c                    |   2 +
 arch/x86/kernel/cpu/intel.c                     | 183 ++++++++++++++++++++++++
 arch/x86/kernel/process.c                       |   3 +
 arch/x86/kernel/traps.c                         |  24 +++-
 9 files changed, 258 insertions(+), 3 deletions(-)