On 18/02/2025 8:39 pm, Rob Herring (Arm) wrote:
This series enables perf branch stack sampling support on arm64 via a v9.2 arch feature called Branch Record Buffer Extension (BRBE). Details on BRBE can be found in the Arm ARM[1] chapter D18. I've picked up this series from Anshuman. v19 and v20 versions have been reworked quite a bit by Mark and myself. The bulk of those changes are in patch 11. Patches 1-7 are new clean-ups/prep which stand on their own. They were previously posted here[2]. Please pick them up if there's no issues with them. Patches 8-11 add BRBE support with the actual support in patch 11. A git branch is here[3]. [1] https://developer.arm.com/documentation/ddi0487/latest/ [2] https://lore.kernel.org/all/20250107-arm-pmu-cleanups-v1-v1-0-313951346a25@xxxxxxxxxx/ [3] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git arm/brbe-v20 v20: - Added back some of the arm64 specific exception types. The x86 IRQ branches also include other exceptions like page faults. On arm64, we can distinguish the exception types, so we do. Also, to better align with x86, we convert 'call' branches which are user to kernel to 'syscall'. - Only enable exceptions and exception returns if recording kernel branches (matching x86) - Drop requiring event and branch privileges to match - Add "branches" caps sysfs attribute like x86 - Reword comment about FZP and MDCR_EL2.HPMN interaction - Rework BRBE invalidation to avoid invalidating in interrupt handler when no handled events capture the branch stack (i.e. when there are multiple users). - Also clear BRBCR_ELx bits in brbe_disable(). This is for KVM nVHE checks if BRBE is enabled. - Document that MDCR_EL3.SBRBE can be 0b01 also
Tested-by: James Clark <james.clark@xxxxxxxxxx>
