AMD Bus Lock Trap Support Merged For Linux 6.13

Going back to early in the year AMD Linux engineers began preparing support for a new Bus Lock Trap feature with Zen 5 CPUs. With the in-development Linux 6.13 kernel that support is being merged.

Years after Intel Linux engineers worked out the split lock detection and bus lock detection for the Linux kernel and their processors to warn or kill on offending applications given the negative performance impact those locks can have on overall system performance, AMD Zen 5 systems running Linux 6.13+ will be able to leverage Bus Lock Trap.

The AMD Bus Lock Trap support with modern Ryzen/EPYC Zen 5 processors is now wired up with Linux 6.13. The Linux kernel code builds off the foundation laid out by Intel engineers. The AMD Bus Lock Trap feature will raise a #DB exception on occurrence of a bus lock when outside of the kernel (ring zero). Knowing about bus/split locks with either a warning or killing the app can be important for overall system performance health.

The work had been queued ahead of Linux 6.12 but the tip/tip.git's x86/splitlock branch ultimately wasn't sent in for the prior merge window. This week though the code was submitted and since merged for Linux 6.13.

With Linux 6.13 the split lock detection and bus lock detection is also now behind a "CONFIG_X86_BUS_LOCK_DETECT" Kconfig build time switch for those wishing to toggle the support. More details on the functionality can be found via the kernel documentation.