Apply dynamic guest counter reservations by checking if the requested guest mask collides with any events the host has scheduled and calling pmu_perf_resched_update() with a hook that updates the mask of available counters in between schedule out and schedule in.
Signed-off-by: Colton Lewis <[email protected]> --- arch/arm64/kvm/pmu-direct.c | 69 ++++++++++++++++++++++++++++++++++++ include/linux/perf/arm_pmu.h | 1 + 2 files changed, 70 insertions(+) diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c index 2252d3b905db9..14cc419dbafad 100644 --- a/arch/arm64/kvm/pmu-direct.c +++ b/arch/arm64/kvm/pmu-direct.c @@ -100,6 +100,73 @@ u8 kvm_pmu_hpmn(struct kvm_vcpu *vcpu) return *host_data_ptr(nr_event_counters); } +/* Callback to update counter mask between perf scheduling */ +static void kvm_pmu_update_mask(struct pmu *pmu, void *data) +{ + struct arm_pmu *arm_pmu = to_arm_pmu(pmu); + unsigned long *new_mask = data; + + bitmap_copy(arm_pmu->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS); +} + +/** + * kvm_pmu_set_guest_counters() - Handle dynamic counter reservations + * @cpu_pmu: struct arm_pmu to potentially modify + * @guest_mask: new guest mask for the pmu + * + * Check if guest counters will interfere with current host events and + * call into perf_pmu_resched_update if a reschedule is required. + */ +static void kvm_pmu_set_guest_counters(struct arm_pmu *cpu_pmu, u64 guest_mask) +{ + struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events); + DECLARE_BITMAP(guest_bitmap, ARMPMU_MAX_HWEVENTS); + DECLARE_BITMAP(new_mask, ARMPMU_MAX_HWEVENTS); + bool need_resched = false; + + bitmap_from_arr64(guest_bitmap, &guest_mask, ARMPMU_MAX_HWEVENTS); + bitmap_copy(new_mask, cpu_pmu->hw_cntr_mask, ARMPMU_MAX_HWEVENTS); + + if (guest_mask) { + /* Subtract guest counters from available host mask */ + bitmap_andnot(new_mask, new_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS); + + /* Did we collide with an active host event? */ + if (bitmap_intersects(cpuc->used_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS)) { + int idx; + + need_resched = true; + cpuc->host_squeezed = true; + + /* Look for pinned events that are about to be preempted */ + for_each_set_bit(idx, guest_bitmap, ARMPMU_MAX_HWEVENTS) { + if (test_bit(idx, cpuc->used_mask) && cpuc->events[idx] && + cpuc->events[idx]->attr.pinned) { + pr_warn_ratelimited("perf: Pinned host event squeezed out by KVM guest PMU partition\n"); + break; + } + } + } + } else { + /* + * Restoring to hw_cntr_mask. + * Only resched if we previously squeezed an event. + */ + if (cpuc->host_squeezed) { + need_resched = true; + cpuc->host_squeezed = false; + } + } + + if (need_resched) { + /* Collision: run full perf reschedule */ + perf_pmu_resched_update(&cpu_pmu->pmu, kvm_pmu_update_mask, new_mask); + } else { + /* Host was never using guest counters anyway */ + bitmap_copy(cpu_pmu->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS); + } +} + /** * kvm_pmu_host_counter_mask() - Compute bitmask of host-reserved counters * @pmu: Pointer to arm_pmu struct @@ -218,6 +285,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu) pmu = vcpu->kvm->arch.arm_pmu; guest_counters = kvm_pmu_guest_counter_mask(pmu); + kvm_pmu_set_guest_counters(pmu, guest_counters); kvm_pmu_apply_event_filter(vcpu); for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) { @@ -319,5 +387,6 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu) val = read_sysreg(pmintenset_el1); __vcpu_assign_sys_reg(vcpu, PMINTENSET_EL1, val & mask); + kvm_pmu_set_guest_counters(pmu, 0); preempt_enable(); } diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h index f7b000bb3eca8..63f88fec5e80f 100644 --- a/include/linux/perf/arm_pmu.h +++ b/include/linux/perf/arm_pmu.h @@ -75,6 +75,7 @@ struct pmu_hw_events { /* Active events requesting branch records */ unsigned int branch_users; + bool host_squeezed; }; enum armpmu_attr_groups { -- 2.54.0.545.g6539524ca2-goog
