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Message-Id: <20250407-arm-brbe-v19-v21-0-ff187ff6c928@kernel.org>
Date: Mon, 07 Apr 2025 12:41:29 -0500
From: "Rob Herring (Arm)" <robh@...nel.org>
To: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
Catalin Marinas <catalin.marinas@....com>, Jonathan Corbet <corbet@....net>,
Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>, James Clark <james.clark@...aro.org>,
Anshuman Khandual <anshuman.khandual@....com>, Leo Yan <leo.yan@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
kvmarm@...ts.linux.dev, Mark Brown <broonie@...nel.org>
Subject: [PATCH v21 0/4] arm64/perf: Enable branch stack sampling
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 4.
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-v21
v21:
- 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@...nel.org>
---
Anshuman Khandual (4):
arm64/sysreg: Add BRBE registers and fields
arm64: Handle BRBE booting requirements
KVM: arm64: nvhe: Disable branch generation in nVHE guests
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 | 86 +++-
arch/arm64/include/asm/kvm_host.h | 2 +
arch/arm64/include/asm/sysreg.h | 17 +-
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 | 802 +++++++++++++++++++++++++++++++++++
drivers/perf/arm_brbe.h | 47 ++
drivers/perf/arm_pmu.c | 15 +-
drivers/perf/arm_pmuv3.c | 129 +++++-
include/linux/perf/arm_pmu.h | 8 +
15 files changed, 1287 insertions(+), 22 deletions(-)
---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250129-arm-brbe-v19-24d5d9e5e623
Best regards,
--
Rob Herring (Arm) <robh@...nel.org>
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