From: Linus Torvalds Date: Mon, 26 Apr 2021 17:09:38 +0000 (-0700) Subject: Merge tag 'x86-splitlock-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel... X-Git-Tag: accepted/tizen/unified/20230118.172025~7424 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=64f8e73de08d11cbe01347340db95b4011872ec5;p=platform%2Fkernel%2Flinux-rpi.git Merge tag 'x86-splitlock-2021-04-26' of git://git./linux/kernel/git/tip/tip 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 --- 64f8e73de08d11cbe01347340db95b4011872ec5