[PATCH v9 13/22] 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@xxxxxxxxxx>
---
 arch/arm64/kvm/pmu-direct.c | 77 +++++++++++++++++++++++++++++++++++++
 arch/arm64/kvm/sys_regs.c   |  1 +
 include/kvm/arm_pmu.h       |  3 ++
 3 files changed, 81 insertions(+)

diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 92eec0fa33867..a22c9258c2452 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -169,6 +169,82 @@ u64 kvm_pmu_guest_counter_mask(void)
 	return kvm_vcpu_pmu_guest_counter_mask(kvm_get_running_vcpu());
 }
 
+/**
+ * kvm_pmu_apply_single_event_filter() - Apply event filter to a single counter
+ * @vcpu: Pointer to vcpu struct
+ * @idx: Counter index
+ *
+ * Compute the filtered event value and write it directly to the hardware register.
+ */
+void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx)
+{
+	struct arm_pmu *pmu = vcpu->kvm->arch.arm_pmu;
+	u64 guest_counters;
+	u64 evtyper_set = ARMV8_PMU_EXCLUDE_EL0 |
+		ARMV8_PMU_EXCLUDE_EL1;
+	u64 evtyper_clr = ARMV8_PMU_INCLUDE_EL2;
+	bool guest_include_el2;
+	u64 val;
+	u64 evsel;
+
+	if (!pmu || vcpu != kvm_get_running_vcpu())
+		return;
+
+	guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+	if (!test_bit(idx, (unsigned long *)&guest_counters))
+		return;
+
+	if (idx == 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 + idx);
+		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))) {
+		if (guest_include_el2)
+			val &= ~ARMV8_PMU_EXCLUDE_EL1;
+		else
+			val |= ARMV8_PMU_EXCLUDE_EL1;
+	}
+
+	if (vcpu->kvm->arch.pmu_filter &&
+	    !test_bit(evsel, vcpu->kvm->arch.pmu_filter))
+		val |= evtyper_set;
+
+	if (idx == ARMV8_PMU_CYCLE_IDX)
+		write_pmccfiltr(val);
+	else
+		write_pmevtypern(idx, val);
+}
+
+/**
+ * kvm_pmu_apply_event_filter() - Apply event filter to all guest counters
+ * @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;
+	u8 i;
+
+	if (!pmu)
+		return;
+
+	guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+
+	for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS)
+		kvm_pmu_apply_single_event_filter(vcpu, i);
+}
+
 /**
  * kvm_pmu_load() - Load untrapped PMU registers
  * @vcpu: Pointer to struct kvm_vcpu
@@ -194,6 +270,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
 	preempt_disable();
 
 	guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+	kvm_pmu_apply_event_filter(vcpu);
 
 	for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
 		val = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index ebcf52261df65..c4aa6a448b6ca 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1137,6 +1137,7 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
 		if (kvm_pmu_is_partitioned(vcpu->kvm)) {
 			mask = kvm_pmu_evtyper_mask(vcpu->kvm);
 			__vcpu_assign_sys_reg(vcpu, reg, val & mask);
+			kvm_pmu_apply_single_event_filter(vcpu, idx);
 		} else {
 			kvm_pmu_set_counter_event_type(vcpu, val, idx);
 			kvm_vcpu_pmu_restore_guest(vcpu);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 2604a6a46d5f3..ddbbbb050b9de 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -104,6 +104,7 @@ u64 kvm_pmu_host_counter_mask(void);
 u64 kvm_pmu_guest_counter_mask(void);
 void kvm_pmu_load(struct kvm_vcpu *vcpu);
 void kvm_pmu_put(struct kvm_vcpu *vcpu);
+void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx);
 
 /*
  * Updates the vcpu's view of the pmu events for this cpu.
@@ -263,6 +264,8 @@ static inline u64 kvm_pmu_guest_counter_mask(void)
 	return 0;
 }
 
+static inline void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx) {}
+
 static inline bool has_kvm_pmu_partition_support(void)
 {
 	return false;
-- 
2.56.0.rc1.310.g51773c2048-goog