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64f8e73de0
Pull x86 bus lock detection updates from Thomas Gleixner: "Support for enhanced split lock detection: Newer CPUs provide a second mechanism to detect operations with lock prefix which go accross a cache line boundary. Such operations have to take bus lock which causes a system wide performance degradation when these operations happen frequently. The new mechanism is not using the #AC exception. It triggers #DB and is restricted to operations in user space. Kernel side split lock access can only be detected by the #AC based variant. Contrary to the #AC based mechanism the #DB based variant triggers _after_ the instruction was executed. The mechanism is CPUID enumerated and contrary to the #AC version which is based on the magic TEST_CTRL_MSR and model/family based enumeration on the way to become architectural" * tag 'x86-splitlock-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/admin-guide: Change doc for split_lock_detect parameter x86/traps: Handle #DB for bus lock x86/cpufeatures: Enumerate #DB for bus lock detection
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.