Subject: [PATCH 4/8] KVM: arm64: Inject UNDEF on PMU access when no PMU configured

From: Marc Zyngier <[email-masked]>
Date: Fri, 13 Nov 2020 18:25:58 +0000

The ARMv8 architecture says that in the absence of FEAT_PMUv3,
all the PMU-related register generate an UNDEF. Let's make
sure that all our PMU handers catch this case by hooking into
check_pmu_access_disabled(), and add checks in a couple of
other places.

Note that we still cannot deliver an exception into the guest
as the offending cases are already caught by the RAZ/WI handling.
But this puts us one step away to architectural compliance.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/kvm/sys_regs.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 6629cfde2838..b098d667bb42 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -609,8 +609,9 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 static bool check_pmu_access_disabled(struct kvm_vcpu *vcpu, u64 flags)
 {
 	u64 reg = __vcpu_sys_reg(vcpu, PMUSERENR_EL0);
-	bool enabled = (reg & flags) || vcpu_mode_priv(vcpu);
+	bool enabled = kvm_vcpu_has_pmu(vcpu);
 
+	enabled &= (reg & flags) || vcpu_mode_priv(vcpu);
 	if (!enabled)
 		kvm_inject_undefined(vcpu);
 
@@ -857,10 +858,8 @@ static bool access_pminten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (!kvm_arm_pmu_v3_ready(vcpu))
 		return trap_raz_wi(vcpu, p, r);
 
-	if (!vcpu_mode_priv(vcpu)) {
-		kvm_inject_undefined(vcpu);
+	if (check_pmu_access_disabled(vcpu, 0))
 		return false;
-	}
 
 	if (p->is_write) {
 		u64 val = p->regval & mask;
@@ -928,6 +927,11 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (!kvm_arm_pmu_v3_ready(vcpu))
 		return trap_raz_wi(vcpu, p, r);
 
+	if (!kvm_vcpu_has_pmu(vcpu)) {
+		kvm_inject_undefined(vcpu);
+		return false;
+	}
+
 	if (p->is_write) {
 		if (!vcpu_mode_priv(vcpu)) {
 			kvm_inject_undefined(vcpu);
-- 
2.28.0

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