Intel Bus Lock Detection Merged For Linux 5.13

Intel's code for Linux kernel bus lock detection that works in conjunction with newer Intel CPUs has landed in the Linux kernel.

Last year Intel contributed split lock detection for Linux 5.7+ for finding out when an atomic instruction ends up spanning multiple cache lines. Those split locks can incur significant performance penalties and now that kernel code has been extended to cover bus lock detection too with Linux 5.13+ on recent Intel processors.

The bus lock detection is important for performance penalties and also possible denial of service reasons. This requires the ability for the processor to notify the kernel after an instruction acquires a bus lock and is executed. When such an event occurs, the kernel implementation allows for throttling the user-space software or stopping the application, similar to the split lock detection handling.

The bus lock detection is handled through the same split_lock_detect= kernel parameter as the split lock detection where off / warn / fatal can be specified.

More details within x86/splitlock that has already been merged into the mainline kernel tree for the Linux 5.13 merge window.