[PATCH v7 11/20] KVM: arm64: Enforce PMU event filter at vcpu_load()

[Colton Lewis]

The KVM API for event filtering says that counters do not count when
blocked by the event filter. To enforce that, the event filter must be
rechecked on every load since it might have changed since the last
time the guest wrote a value. If the event is filtered, exclude
counting at all exception levels before writing the hardware.

Signed-off-by: Colton Lewis <coltonlewis at google.com>
---
 arch/arm64/kvm/pmu-direct.c | 54 +++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 360d022d918d5..2252d3b905db9 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -138,6 +138,59 @@ u64 kvm_pmu_guest_counter_mask(struct arm_pmu *pmu)
 	return 0;
 }
 
+/**
+ * kvm_pmu_apply_event_filter()
+ * @vcpu: Pointer to vcpu struct
+ *
+ * To uphold the guarantee of the KVM PMU event filter, we must ensure
+ * no counter counts if the event is filtered. Accomplish this by
+ * filtering all exception levels if the event is filtered.
+ */
+static void kvm_pmu_apply_event_filter(struct kvm_vcpu *vcpu)
+{
+	struct arm_pmu *pmu = vcpu->kvm->arch.arm_pmu;
+	unsigned long guest_counters;
+	u64 evtyper_set = ARMV8_PMU_EXCLUDE_EL0 |
+		ARMV8_PMU_EXCLUDE_EL1;
+	u64 evtyper_clr = ARMV8_PMU_INCLUDE_EL2;
+	bool guest_include_el2;
+	u8 i;
+	u64 val;
+	u64 evsel;
+
+	if (!pmu)
+		return;
+
+	guest_counters = kvm_pmu_guest_counter_mask(pmu);
+
+	for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
+		if (i == ARMV8_PMU_CYCLE_IDX) {
+			val = __vcpu_sys_reg(vcpu, PMCCFILTR_EL0);
+			evsel = ARMV8_PMUV3_PERFCTR_CPU_CYCLES;
+		} else {
+			val = __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + i);
+			evsel = val & kvm_pmu_event_mask(vcpu->kvm);
+		}
+
+		guest_include_el2 = (val & ARMV8_PMU_INCLUDE_EL2);
+		val &= ~evtyper_clr;
+
+		if (unlikely(is_hyp_ctxt(vcpu)) && guest_include_el2)
+			val &= ~ARMV8_PMU_EXCLUDE_EL1;
+
+		if (vcpu->kvm->arch.pmu_filter &&
+		    !test_bit(evsel, vcpu->kvm->arch.pmu_filter))
+			val |= evtyper_set;
+
+		if (i == ARMV8_PMU_CYCLE_IDX) {
+			write_sysreg(val, pmccntr_el0);
+		} else {
+			write_sysreg(i, pmselr_el0);
+			write_sysreg(val, pmxevtyper_el0);
+		}
+	}
+}
+
 /**
  * kvm_pmu_load() - Load untrapped PMU registers
  * @vcpu: Pointer to struct kvm_vcpu
@@ -165,6 +218,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
 
 	pmu = vcpu->kvm->arch.arm_pmu;
 	guest_counters = kvm_pmu_guest_counter_mask(pmu);
+	kvm_pmu_apply_event_filter(vcpu);
 
 	for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
 		val = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i);
-- 
2.54.0.545.g6539524ca2-goog