linux-kernel - [RFC 2/3] KVM: arm64: pmu: Fix chained SW

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Message-Id: <20191204204426.9628-3-eric.auger@redhat.com>
Date:   Wed,  4 Dec 2019 21:44:25 +0100
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Cc:     james.morse@....com, andrew.murray@....com, suzuki.poulose@....com,
        drjones@...hat.com
Subject: [RFC 2/3] KVM: arm64: pmu: Fix chained SW_INCR counters

At the moment a SW_INCR counter always overflows on 32-bit
boundary, independently on whether the n+1th counter is
programmed as CHAIN.

Check whether the SW_INCR counter is a 64b counter and if so,
implement the 64b logic.

Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters")
Signed-off-by: Eric Auger <eric.auger@...hat.com>
---
 virt/kvm/arm/pmu.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index c3f8b059881e..7ab477db2f75 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -491,6 +491,8 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
 
 	enable = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
 	for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++) {
+		bool chained = test_bit(i >> 1, vcpu->arch.pmu.chained);
+
 		if (!(val & BIT(i)))
 			continue;
 		type = __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + i)
@@ -500,8 +502,20 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
 			reg = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) + 1;
 			reg = lower_32_bits(reg);
 			__vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) = reg;
-			if (!reg)
+			if (reg) /* no overflow */
+				continue;
+			if (chained) {
+				reg = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i + 1) + 1;
+				reg = lower_32_bits(reg);
+				__vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i + 1) = reg;
+				if (reg)
+					continue;
+				/* mark an overflow on high counter */
+				__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i + 1);
+			} else {
+				/* mark an overflow */
 				__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i);
+			}
 		}
 	}
 }
-- 
2.20.1