From: Andrew Murray <andrew.murray@arm.com> To: Christoffer Dall <christoffer.dall@arm.com>, Marc Zyngier <marc.zyngier@arm.com> Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: [PATCH v9 0/5] KVM: arm/arm64: add support for chained counters Date: Wed, 12 Jun 2019 20:04:45 +0100 [thread overview] Message-ID: <20190612190450.7085-1-andrew.murray@arm.com> (raw) ARMv8 provides support for chained PMU counters, where an event type of 0x001E is set for odd-numbered counters, the event counter will increment by one for each overflow of the preceding even-numbered counter. Let's emulate this in KVM by creating a 64 bit perf counter when a user chains two emulated counters together. Testing has been performed by hard-coding hwc->sample_period in __hw_perf_event_init (arm_pmu.c) to a small value, this results in regular overflows (for non sampling events). The following command was then used to measure chained and non-chained instruction cycles: perf stat -e armv8_pmuv3/long=1,inst_retired/u \ -e armv8_pmuv3/long=0,inst_retired/u dd if=/dev/zero bs=1M \ count=10 | gzip > /dev/null The reported values were identical (and for non-chained was in the same ballpark when running on a kernel without this patchset). Debug was added to verify that the guest received overflow interrupts for the chain counter. The test was also repeated using the cycle counter (cycle:u). For chained events we only support generating an overflow interrupt on the high counter. We use the attributes of the low counter to determine the attributes of the perf event. Changes since v8: - Correctly calculate the sample_period for the cycle counter - Drop "arm64: perf: extract chain helper into header" patch Changes since v7: - Remove pmc->bitmask - Remove a couple of instances of using kvm_pmu_get_canonical_pmc when not needed - Remove unused perf_event variable Changes since v6: - Drop kvm_pmu_{get,set}_perf_event - Avoid duplicate work by using kvm_pmu_get_pair_counter_value inside kvm_pmu_stop_counter - Use GENMASK for 64bit mask Changes since v5: - Use kvm_pmu_pmc_is_high_counter instead of open coding - Rename kvm_pmu_event_is_chained to kvm_pmu_idx_has_chain_evtype - Use kvm_pmu_get_canonical_pmc only where needed and reintroduce the kvm_pmu_{set, get}_perf_event functions - Drop masking of counter in kvm_pmu_get_pair_counter_value - Only initialise pmc once in kvm_pmu_create_perf_event and other minor changes. Changes since v4: - Track pairs of chained counters with a bitmap instead of using a struct kvm_pmc_pair. - Rebase onto kvmarm/queue Changes since v3: - Simplify approach by not creating events lazily and by introducing a struct kvm_pmc_pair to represent the relationship between adjacent counters. - Rebase onto v5.1-rc2 Changes since v2: - Rebased onto v5.0-rc7 - Add check for cycle counter in correct patch - Minor style, naming and comment changes - Extract armv8pmu_evtype_is_chain from arch/arm64/kernel/perf_event.c into a common header that KVM can use Changes since v1: - Rename kvm_pmu_{enable,disable}_counter to reflect that they can operate on multiple counters at once and use these functions where possible - Fix bugs with overflow handing, kvm_pmu_get_counter_value did not take into consideration the perf counter value overflowing the low counter - Ensure PMCCFILTR_EL0 is used when operating on the cycle counter - Rename kvm_pmu_reenable_enabled_{pair, single} and similar - Always create perf event disabled to simplify logic elsewhere - Move PMCNTENSET_EL0 test to kvm_pmu_enable_counter_mask Andrew Murray (5): KVM: arm/arm64: rename kvm_pmu_{enable/disable}_counter functions KVM: arm/arm64: extract duplicated code to own function KVM: arm/arm64: re-create event when setting counter value KVM: arm/arm64: remove pmc->bitmask KVM: arm/arm64: support chained PMU counters arch/arm64/kvm/sys_regs.c | 4 +- include/kvm/arm_pmu.h | 11 +- virt/kvm/arm/pmu.c | 340 ++++++++++++++++++++++++++++++-------- 3 files changed, 281 insertions(+), 74 deletions(-) -- 2.21.0 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Murray <andrew.murray@arm.com> To: Christoffer Dall <christoffer.dall@arm.com>, Marc Zyngier <marc.zyngier@arm.com> Cc: Suzuki K Pouloze <suzuki.poulose@arm.com>, James Morse <james.morse@arm.com>, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Julien Thierry <julien.thierry@arm.com> Subject: [PATCH v9 0/5] KVM: arm/arm64: add support for chained counters Date: Wed, 12 Jun 2019 20:04:45 +0100 [thread overview] Message-ID: <20190612190450.7085-1-andrew.murray@arm.com> (raw) ARMv8 provides support for chained PMU counters, where an event type of 0x001E is set for odd-numbered counters, the event counter will increment by one for each overflow of the preceding even-numbered counter. Let's emulate this in KVM by creating a 64 bit perf counter when a user chains two emulated counters together. Testing has been performed by hard-coding hwc->sample_period in __hw_perf_event_init (arm_pmu.c) to a small value, this results in regular overflows (for non sampling events). The following command was then used to measure chained and non-chained instruction cycles: perf stat -e armv8_pmuv3/long=1,inst_retired/u \ -e armv8_pmuv3/long=0,inst_retired/u dd if=/dev/zero bs=1M \ count=10 | gzip > /dev/null The reported values were identical (and for non-chained was in the same ballpark when running on a kernel without this patchset). Debug was added to verify that the guest received overflow interrupts for the chain counter. The test was also repeated using the cycle counter (cycle:u). For chained events we only support generating an overflow interrupt on the high counter. We use the attributes of the low counter to determine the attributes of the perf event. Changes since v8: - Correctly calculate the sample_period for the cycle counter - Drop "arm64: perf: extract chain helper into header" patch Changes since v7: - Remove pmc->bitmask - Remove a couple of instances of using kvm_pmu_get_canonical_pmc when not needed - Remove unused perf_event variable Changes since v6: - Drop kvm_pmu_{get,set}_perf_event - Avoid duplicate work by using kvm_pmu_get_pair_counter_value inside kvm_pmu_stop_counter - Use GENMASK for 64bit mask Changes since v5: - Use kvm_pmu_pmc_is_high_counter instead of open coding - Rename kvm_pmu_event_is_chained to kvm_pmu_idx_has_chain_evtype - Use kvm_pmu_get_canonical_pmc only where needed and reintroduce the kvm_pmu_{set, get}_perf_event functions - Drop masking of counter in kvm_pmu_get_pair_counter_value - Only initialise pmc once in kvm_pmu_create_perf_event and other minor changes. Changes since v4: - Track pairs of chained counters with a bitmap instead of using a struct kvm_pmc_pair. - Rebase onto kvmarm/queue Changes since v3: - Simplify approach by not creating events lazily and by introducing a struct kvm_pmc_pair to represent the relationship between adjacent counters. - Rebase onto v5.1-rc2 Changes since v2: - Rebased onto v5.0-rc7 - Add check for cycle counter in correct patch - Minor style, naming and comment changes - Extract armv8pmu_evtype_is_chain from arch/arm64/kernel/perf_event.c into a common header that KVM can use Changes since v1: - Rename kvm_pmu_{enable,disable}_counter to reflect that they can operate on multiple counters at once and use these functions where possible - Fix bugs with overflow handing, kvm_pmu_get_counter_value did not take into consideration the perf counter value overflowing the low counter - Ensure PMCCFILTR_EL0 is used when operating on the cycle counter - Rename kvm_pmu_reenable_enabled_{pair, single} and similar - Always create perf event disabled to simplify logic elsewhere - Move PMCNTENSET_EL0 test to kvm_pmu_enable_counter_mask Andrew Murray (5): KVM: arm/arm64: rename kvm_pmu_{enable/disable}_counter functions KVM: arm/arm64: extract duplicated code to own function KVM: arm/arm64: re-create event when setting counter value KVM: arm/arm64: remove pmc->bitmask KVM: arm/arm64: support chained PMU counters arch/arm64/kvm/sys_regs.c | 4 +- include/kvm/arm_pmu.h | 11 +- virt/kvm/arm/pmu.c | 340 ++++++++++++++++++++++++++++++-------- 3 files changed, 281 insertions(+), 74 deletions(-) -- 2.21.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2019-06-12 19:05 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-12 19:04 Andrew Murray [this message] 2019-06-12 19:04 ` [PATCH v9 0/5] KVM: arm/arm64: add support for chained counters Andrew Murray 2019-06-12 19:04 ` [PATCH v9 1/5] KVM: arm/arm64: rename kvm_pmu_{enable/disable}_counter functions Andrew Murray 2019-06-12 19:04 ` Andrew Murray 2019-06-12 19:04 ` [PATCH v9 2/5] KVM: arm/arm64: extract duplicated code to own function Andrew Murray 2019-06-12 19:04 ` Andrew Murray 2019-06-12 19:04 ` [PATCH v9 3/5] KVM: arm/arm64: re-create event when setting counter value Andrew Murray 2019-06-12 19:04 ` Andrew Murray 2019-06-12 19:04 ` [PATCH v9 4/5] KVM: arm/arm64: remove pmc->bitmask Andrew Murray 2019-06-12 19:04 ` Andrew Murray 2019-06-13 7:30 ` Julien Thierry 2019-06-13 7:30 ` Julien Thierry 2019-06-13 9:39 ` Andrew Murray 2019-06-13 9:39 ` Andrew Murray 2019-06-13 16:50 ` Suzuki K Poulose 2019-06-13 16:50 ` Suzuki K Poulose 2019-06-17 15:43 ` Andrew Murray 2019-06-17 15:43 ` Andrew Murray 2019-06-17 16:33 ` Suzuki K Poulose 2019-06-17 16:33 ` Suzuki K Poulose 2019-06-17 18:06 ` Andrew Murray 2019-06-17 18:06 ` Andrew Murray 2019-06-12 19:04 ` [PATCH v9 5/5] KVM: arm/arm64: support chained PMU counters Andrew Murray 2019-06-12 19:04 ` Andrew Murray 2019-06-14 12:08 ` Suzuki K Poulose 2019-06-14 12:08 ` Suzuki K Poulose
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