KVM: arm64: Mask out filtered events in PCMEID{0,1}_EL1

As we can now hide events from the guest, let's also adjust its view of
PCMEID{0,1}_EL1 so that it can figure out why some common events are not
counting as they should.

The astute user can still look into the TRM for their CPU and find out
they've been cheated, though. Nobody's perfect.
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/pmu-emul.c

@@ -763,6 +763,35 @@ static int kvm_pmu_probe_pmuver(void)
 	return pmuver;
 }
 
+u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
+{
+	unsigned long *bmap = vcpu->kvm->arch.pmu_filter;
+	u64 val, mask = 0;
+	int base, i;
+
+	if (!pmceid1) {
+		val = read_sysreg(pmceid0_el0);
+		base = 0;
+	} else {
+		val = read_sysreg(pmceid1_el0);
+		base = 32;
+	}
+
+	if (!bmap)
+		return val;
+
+	for (i = 0; i < 32; i += 8) {
+		u64 byte;
+
+		byte = bitmap_get_value8(bmap, base + i);
+		mask |= byte << i;
+		byte = bitmap_get_value8(bmap, 0x4000 + base + i);
+		mask |= byte << (32 + i);
+	}
+
+	return val & mask;
+}
+
 bool kvm_arm_support_pmu_v3(void)
 {
 	/*

arch/arm64/kvm/sys_regs.c

@@ -769,10 +769,7 @@ static bool access_pmceid(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (pmu_access_el0_disabled(vcpu))
 		return false;
 
-	if (!(p->Op2 & 1))
-		pmceid = read_sysreg(pmceid0_el0);
-	else
-		pmceid = read_sysreg(pmceid1_el0);
+	pmceid = kvm_pmu_get_pmceid(vcpu, (p->Op2 & 1));
 
 	p->regval = pmceid;
 

include/kvm/arm_pmu.h

@@ -34,6 +34,7 @@ struct kvm_pmu {
 u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
 void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
 u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu);
+u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1);
 void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
 void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
 void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
@@ -108,6 +109,10 @@ static inline int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu)
 {
 	return 0;
 }
+static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
+{
+	return 0;
+}
 #endif
 
 #endif