From 9e3f7a29694049edd728e2400ab57ad7553e5aa9 Mon Sep 17 00:00:00 2001
From: Wei Huang <wei@redhat.com>
Date: Wed, 16 Nov 2016 09:20:57 +0000
Subject: arm64: KVM: pmu: Fix AArch32 cycle counter access

We're missing the handling code for the cycle counter accessed
from a 32bit guest, leading to unexpected results.

Cc: stable@vger.kernel.org # 4.6+
Signed-off-by: Wei Huang <wei@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f302fdb..87e7e66 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -597,8 +597,14 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
 
 			idx = ARMV8_PMU_CYCLE_IDX;
 		} else {
-			BUG();
+			return false;
 		}
+	} else if (r->CRn == 0 && r->CRm == 9) {
+		/* PMCCNTR */
+		if (pmu_access_event_counter_el0_disabled(vcpu))
+			return false;
+
+		idx = ARMV8_PMU_CYCLE_IDX;
 	} else if (r->CRn == 14 && (r->CRm & 12) == 8) {
 		/* PMEVCNTRn_EL0 */
 		if (pmu_access_event_counter_el0_disabled(vcpu))
@@ -606,7 +612,7 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
 
 		idx = ((r->CRm & 3) << 3) | (r->Op2 & 7);
 	} else {
-		BUG();
+		return false;
 	}
 
 	if (!pmu_counter_idx_valid(vcpu, idx))
-- 
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