• Linus Torvalds's avatar
    Merge tag 'x86-splitlock-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 2853d5fa
    Linus Torvalds authored
    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
    2853d5fa
traps.c 28.6 KB