Hi Rob, Thanks again for this. On Wed, Jun 11, 2025 at 01:01:10PM -0500, 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 later versions have > been reworked quite a bit by Mark and myself. The bulk of those changes > are in patch 5. Aside from the comments on patch 4, this all looks good to me, and for the series: Acked-by: Mark Rutland <mark.rutland@xxxxxxx> I assume that Will will pick this up soon. Mark. > > A git branch is here[2]. > > [1] https://developer.arm.com/documentation/ddi0487/latest/ > [2] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git arm/brbe-v23 > > v23: > - Rebase on v6.16-rc1 dropping already applied el2_setup.h clean-ups > - Drop the SYSCALL fixup and convert all BRBE CALL events to SYSCALL > > v22: > - https://lore.kernel.org/all/20250520-arm-brbe-v19-v22-0-c1ddde38e7f8@xxxxxxxxxx/ > - New patch reworking the labels in el2_setup.h > - Move branch stack disabling after armpmu_stop() in armpmu_del() > - Fix branch_records_alloc() to work on heterogeneous systems > - Make setting .sched_task function ptr conditional on BRBE support > - Reword booting.rst section name (s/feature/the/) and move next to > other PMU related features instead of in the middle of SME features. > - Drop setting SYS_BRBCR_EL1 > - Drop CONFIG_ARM64_BRBE ifdef > - Rework initialization of HFGITR_EL2 > > v21: > - https://lore.kernel.org/r/20250407-arm-brbe-v19-v21-0-ff187ff6c928@xxxxxxxxxx > - Drop clean-up patches 1-7 already applied > - Rebase on v6.15-rc1 > > v20: > - https://lore.kernel.org/r/20250218-arm-brbe-v19-v20-0-4e9922fc2e8e@xxxxxxxxxx > - 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 > > v19: > - https://lore.kernel.org/all/20250202-arm-brbe-v19-v19-0-1c1300802385@xxxxxxxxxx/ > - Drop saving of branch records when task scheduled out (Mark). Make > sched_task() callback actually get called. Enabling requires a call > to perf_sched_cb_inc(). So the saving of branch records never > happened. > - Got rid of added armpmu ops. All BRBE support is contained within > pmuv3 code. > - Fix freeze on overflow for VHE > - The cycle counter doesn't freeze BRBE on overflow, so avoid assigning > it when BRBE is enabled. > - Drop all the Arm specific exception branches. Not a clear need for > them. > - Fix handling of branch 'cycles' reading. CC field is > mantissa/exponent, not an integer. > - Rework s/w filtering to better match h/w filtering > - Reject events with disjoint event filter and branch filter or with > exclude_host set > - Dropped perf test patch which has been applied for 6.14 > - Dropped patch "KVM: arm64: Explicitly handle BRBE traps as UNDEFINED" > which has been applied for 6.14 > > v18: > - https://lore.kernel.org/all/20240613061731.3109448-1-anshuman.khandual@xxxxxxx/ > > For v1-v17, see the above link. Not going to duplicate it all here... > > Signed-off-by: "Rob Herring (Arm)" <robh@xxxxxxxxxx> > --- > --- > Anshuman Khandual (3): > arm64/sysreg: Add BRBE registers and fields > arm64: Handle BRBE booting requirements > KVM: arm64: nvhe: Disable branch generation in nVHE guests > > Rob Herring (Arm) (1): > perf: arm_pmuv3: Add support for the Branch Record Buffer Extension (BRBE) > > Documentation/arch/arm64/booting.rst | 21 + > arch/arm64/include/asm/el2_setup.h | 71 +++- > arch/arm64/include/asm/kvm_host.h | 2 + > arch/arm64/include/asm/sysreg.h | 16 +- > arch/arm64/kvm/debug.c | 4 + > arch/arm64/kvm/hyp/nvhe/debug-sr.c | 32 ++ > arch/arm64/kvm/hyp/nvhe/switch.c | 2 +- > arch/arm64/tools/sysreg | 132 ++++++ > drivers/perf/Kconfig | 11 + > drivers/perf/Makefile | 1 + > drivers/perf/arm_brbe.c | 798 +++++++++++++++++++++++++++++++++++ > drivers/perf/arm_brbe.h | 47 +++ > drivers/perf/arm_pmu.c | 16 +- > drivers/perf/arm_pmuv3.c | 125 +++++- > include/linux/perf/arm_pmu.h | 8 + > 15 files changed, 1265 insertions(+), 21 deletions(-) > --- > base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494 > change-id: 20250129-arm-brbe-v19-24d5d9e5e623 > > Best regards, > -- > Rob Herring (Arm) <robh@xxxxxxxxxx> >
