[v5,0/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters

Message

Andrew Murray Jan. 27, 2020, 11:44 a.m. UTC

At present ARMv8 event counters are limited to 32-bits, though by
using the CHAIN event it's possible to combine adjacent counters to
achieve 64-bits. The perf config1:0 bit can be set to use such a
configuration.

With the introduction of ARMv8.5-PMU support, all event counters can
now be used as 64-bit counters. Let's add support for 64-bit event
counters.

As KVM doesn't yet support 64-bit event counters (or other features
after PMUv3 for ARMv8.1), we also trap and emulate the Debug Feature
Registers to limit the PMU version a guest sees to PMUv3 for ARMv8.1.

Tested by running the following perf command on both guest and host
and ensuring that the figures are very similar:

perf stat -e armv8_pmuv3/inst_retired,long=1/ \
          -e armv8_pmuv3/inst_retired,long=0/ -e cycles

Changes since v4:

 - Limit KVM to PMUv3 for ARMv8.1 instead of 8.4
 - Reword second commit

Changes since v3:

 - Rebased onto v5.5-rc7
 - Instead of overriding trap access handler, update read_id_reg

Changes since v2:

 - Rebased onto v5.5-rc4
 - Mask 'cap' value to 'width' in cpuid_feature_cap_signed_field_width

Changes since v1:

 - Rebased onto v5.5-rc1



Andrew Murray (3):
  arm64: cpufeature: Extract capped fields
  KVM: arm64: limit PMU version to PMUv3 for ARMv8.1
  arm64: perf: Add support for ARMv8.5-PMU 64-bit counters

 arch/arm64/include/asm/cpufeature.h | 16 +++++++
 arch/arm64/include/asm/perf_event.h |  3 +-
 arch/arm64/include/asm/sysreg.h     |  6 +++
 arch/arm64/kernel/perf_event.c      | 86 +++++++++++++++++++++++++++++--------
 arch/arm64/kvm/sys_regs.c           | 11 +++++
 include/linux/perf/arm_pmu.h        |  1 +
 6 files changed, 105 insertions(+), 18 deletions(-)