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, we also trap and emulate the Debug Feature Registers to limit the PMU version a guest sees to PMUv3 for ARMv8.4. 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 Andrew Murray (3): arm64: cpufeature: Extract capped fields KVM: arm64: limit PMU version to ARMv8.4 arm64: perf: Add support for ARMv8.5-PMU 64-bit counters arch/arm64/include/asm/cpufeature.h | 15 +++++ arch/arm64/include/asm/perf_event.h | 3 +- arch/arm64/include/asm/sysreg.h | 4 ++ arch/arm64/kernel/perf_event.c | 86 +++++++++++++++++++++++------ arch/arm64/kvm/sys_regs.c | 36 +++++++++++- include/linux/perf/arm_pmu.h | 1 + 6 files changed, 125 insertions(+), 20 deletions(-) -- 2.21.0 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm