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(-)
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.
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@kernel.org/
- 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@kernel.org
- 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@kernel.org
- 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@kernel.org/
- 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@arm.com/
For v1-v17, see the above link. Not going to duplicate it all here...
Signed-off-by: "Rob Herring (Arm)" <robh@kernel.org>
---
---
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@kernel.org>
On Wed, 11 Jun 2025 13:01:10 -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.
>
> [...]
Applied to will (for-next/perf), thanks!
[1/4] arm64/sysreg: Add BRBE registers and fields
https://git.kernel.org/will/c/52e4a56ab8b8
[2/4] arm64: Handle BRBE booting requirements
https://git.kernel.org/will/c/ae344bcb0d49
[3/4] KVM: arm64: nvhe: Disable branch generation in nVHE guests
https://git.kernel.org/will/c/d7567e9b9ba5
[4/4] perf: arm_pmuv3: Add support for the Branch Record Buffer Extension (BRBE)
https://git.kernel.org/will/c/58074a0fce66
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
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@arm.com> 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@kernel.org/ > - 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@kernel.org > - 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@kernel.org > - 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@kernel.org/ > - 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@arm.com/ > > For v1-v17, see the above link. Not going to duplicate it all here... > > Signed-off-by: "Rob Herring (Arm)" <robh@kernel.org> > --- > --- > 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@kernel.org> >
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