Linux perf/x86/amd/core - Branch Sampling enabled from the SVM reload path: Branch Sampling and Last Branch Record

Impact

Branch Sampling and Last Branch Record are mutually exclusive, and the KVM/SVM reload path could enable BRS anyway. Conflicting branch-tracing state on a virtualisation host means corrupted profiling data and, on the SVM path, incorrect state restored around guest entry - a correctness problem sitting on the boundary between host and guest execution.

Who can reach it

Local, on hosts running KVM guests with branch sampling in use.

What to do

Distro kernel update plus reboot.

References