tree fc8243bcf4a75902ef843ec65fc06a9d65b187e1
parent d5f744f9a2ac9ca6d5baf72e97ce6dc4c2f19fe4
parent a6a60741035bb48ca8d9f92a138958818148064c
author Linus Torvalds <torvalds@linux-foundation.org> 1585622152 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1585622152 -0700
mergetag object a6a60741035bb48ca8d9f92a138958818148064c
 type commit
 tag x86-splitlock-2020-03-30
 tagger Thomas Gleixner <tglx@linutronix.de> 1585577699 +0200
 
 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.
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Merge tag 'x86-splitlock-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 splitlock updates from Thomas Gleixner:
 "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"

* tag 'x86-splitlock-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR
  x86/split_lock: Rework the initialization flow of split lock detection
  x86/split_lock: Enable split lock detection by kernel