This series introduces support in the KVM and ARM PMUv3 driver for
partitioning PMU counters into two separate ranges by taking advantage
of the MDCR_EL2.HPMN register field.
The advantage of a partitioned PMU would be to allow KVM guests direct
access to a subset of PMU functionality, greatly reducing the overhead
of performance monitoring in guests.
While this feature could be accepted on its own merits, practically
there is a lot more to be done before it will be fully useful, so I'm
sending as an RFC for now.
v3:
* Include cpucap definition for FEAT_HPMN0 to allow for setting HPMN
to 0
* Include PMU header cleanup provided by Marc [1] with some minor
changes so compilation works
* Pull functions out of pmu-emul.c that aren't specific to the
emulated PMU. This and the previous item aren't strictly
needed but they provide a nicer starting point.
* As suggested by Oliver, start a file for partitioned PMU functions
and move the reserved_host_counters parameter and MDCR handling into
KVM so the driver does not have to know about it and we need fewer
hacks to keep the driver working on 32-bit ARM. This was not a
complete separation because the driver still needs to start and stop
the host counters all at once and needs to toggle MDCR_EL2.HPME to
do that. Introduce kvm_pmu_host_counters_{enable,disable}()
functions to handle this and define them as no ops on 32-bit ARM.
* As suggested by Oliver, don't limit PMCR.N on emulated PMU. This
value will be read correctly when the right traps are disabled to
use the partitioned PMU
v2:
https://lore.kernel.org/kvm/20250208020111.2068239-1-coltonle...@google.com/
v1:
https://lore.kernel.org/kvm/20250127222031.3078945-1-coltonle...@google.com/
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/pmu-includes
Colton Lewis (7):
arm64: cpufeature: Add cap for HPMN0
arm64: Generate sign macro for sysreg Enums
KVM: arm64: Reorganize PMU functions
KVM: arm64: Introduce module param to partition the PMU
perf: arm_pmuv3: Generalize counter bitmasks
perf: arm_pmuv3: Keep out of guest counter partition
KVM: arm64: selftests: Reword selftests error
Marc Zyngier (1):
KVM: arm64: Cleanup PMU includes
arch/arm/include/asm/arm_pmuv3.h | 2 +
arch/arm64/include/asm/arm_pmuv3.h | 2 +-
arch/arm64/include/asm/kvm_host.h | 199 +++++++-
arch/arm64/include/asm/kvm_pmu.h | 47 ++
arch/arm64/kernel/cpufeature.c | 8 +
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/arm.c | 1 -
arch/arm64/kvm/debug.c | 10 +-
arch/arm64/kvm/hyp/include/hyp/switch.h | 1 +
arch/arm64/kvm/pmu-emul.c | 464 +-----------------
arch/arm64/kvm/pmu-part.c | 63 +++
arch/arm64/kvm/pmu.c | 454 +++++++++++++++++
arch/arm64/kvm/sys_regs.c | 2 +
arch/arm64/tools/cpucaps | 1 +
arch/arm64/tools/gen-sysreg.awk | 1 +
arch/arm64/tools/sysreg | 6 +-
drivers/perf/arm_pmuv3.c | 73 ++-
include/kvm/arm_pmu.h | 204 --------
include/linux/perf/arm_pmu.h | 16 +-
include/linux/perf/arm_pmuv3.h | 27 +-
.../selftests/kvm/arm64/vpmu_counter_access.c | 2 +-
virt/kvm/kvm_main.c | 1 +
22 files changed, 882 insertions(+), 704 deletions(-)
create mode 100644 arch/arm64/include/asm/kvm_pmu.h
create mode 100644 arch/arm64/kvm/pmu-part.c
delete mode 100644 include/kvm/arm_pmu.h
base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
--
2.48.1.601.g30ceb7b040-goog
