[00/18] KVM: arm64: Support FEAT_PMUv3 on Apple hardware

Message

Oliver Upton Dec. 17, 2024, 9:20 p.m. UTC

One of the interesting features of some Apple M* parts is an IMPDEF trap
that routes EL1/EL0 accesses of the PMUv3 registers to EL2. This allows
a hypervisor to emulate an architectural PMUv3 on top of the IMPDEF PMU
hardware present in the CPU.

And if you squint, this _might_ look like a CPU erratum :-)

This series takes advantage of these IMPDEF traps to provide PMUv3 to
KVM guests. As a starting point, only expose the fixed CPU cycle counter
and no event counters. Conveniently, this is enough to get Windows
running as a KVM guest on Apple hardware.

I've tried to keep the deviation to a minimum by refactoring some of the
flows used for PMUv3, e.g. computing PMCEID from the arm_pmu bitmap
instead of reading hardware directly.

RFC -> v1:
 - Rebase to 6.13-rc3
 - Add support for 1 event counter in addition to CPU cycle counter
 - Don't sneak past the PMU event filter (Marc)
 - Have the PMU driver provide a PMUv3 -> HW event ID mapping (Marc)

Tested on my M2 with Linux and Windows guests. If possible, I'd
appreciate someone testing on an M1 as I haven't added those MIDRs to
the erratum yet.

Oliver Upton (18):
  drivers/perf: apple_m1: Refactor event select/filter configuration
  drivers/perf: apple_m1: Support host/guest event filtering
  drivers/perf: apple_m1: Map generic branch events
  drivers/perf: apple_m1: Provide helper for mapping PMUv3 events
  KVM: arm64: Compute PMCEID from arm_pmu's event bitmaps
  KVM: arm64: Always support SW_INCR PMU event
  KVM: arm64: Remap PMUv3 events onto hardware
  KVM: arm64: Use a cpucap to determine if system supports FEAT_PMUv3
  KVM: arm64: Drop kvm_arm_pmu_available static key
  KVM: arm64: Use guard() to cleanup usage of arm_pmus_lock
  KVM: arm64: Move PMUVer filtering into KVM code
  KVM: arm64: Compute synthetic sysreg ESR for Apple PMUv3 traps
  KVM: arm64: Advertise PMUv3 if IMPDEF traps are present
  KVM: arm64: Advertise 0 event counters for IMPDEF PMU
  arm64: Enable IMP DEF PMUv3 traps on Apple M2
  drivers/perf: apple_m1: Map a few more PMUv3 events
  KVM: arm64: Provide 1 event counter on IMPDEF hardware
  KVM: arm64: selftests: Add test for probing PMUv3 sysregs

 arch/arm64/include/asm/apple_m1_pmu.h         |   1 +
 arch/arm64/include/asm/cpufeature.h           |  28 +---
 arch/arm64/kernel/cpu_errata.c                |  38 +++++
 arch/arm64/kernel/cpufeature.c                |  19 +++
 arch/arm64/kernel/image-vars.h                |   5 -
 arch/arm64/kvm/arm.c                          |   4 +-
 arch/arm64/kvm/hyp/include/hyp/switch.h       |   4 +-
 arch/arm64/kvm/hyp/vhe/switch.c               |  22 +++
 arch/arm64/kvm/pmu-emul.c                     | 127 +++++++++++-----
 arch/arm64/kvm/pmu.c                          |  10 +-
 arch/arm64/tools/cpucaps                      |   2 +
 drivers/perf/apple_m1_cpu_pmu.c               | 103 ++++++++++---
 include/kvm/arm_pmu.h                         |  15 +-
 include/linux/perf/arm_pmu.h                  |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../kvm/aarch64/pmuv3_register_probe.c        | 135 ++++++++++++++++++
 16 files changed, 407 insertions(+), 108 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/aarch64/pmuv3_register_probe.c


base-commit: 78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8