linux-kernel - [PATCH v2] KVM: arm64: pmu: Don't increment SW

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Message-Id: <20200302104830.5593-1-eric.auger@redhat.com>
Date:   Mon,  2 Mar 2020 11:48:30 +0100
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com,
        stable@...r.kernel.org, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Subject: [PATCH v2] KVM: arm64: pmu: Don't increment SW_INCR if PMCR.E is unset

commit 3837407c1aa1 upstream.

The specification says PMSWINC increments PMEVCNTR<n>_EL1 by 1
if PMEVCNTR<n>_EL0 is enabled and configured to count SW_INCR.

For PMEVCNTR<n>_EL0 to be enabled, we need both PMCNTENSET to
be set for the corresponding event counter but we also need
the PMCR.E bit to be set.

Fixes: 7a0adc7064b8 ("arm64: KVM: Add access handler for PMSWINC register")
Signed-off-by: Eric Auger <eric.auger@...hat.com>
Cc: <stable@...r.kernel.org> # 4.9 and 4.14 only

---

This is a backport of 3837407c1aa1 ("KVM: arm64: pmu: Don't
increment SW_INCR if PMCR.E is unset") which did not apply on
4.9-stable and 4.14-stable trees. Compared to the original patch
__vcpu_sys_reg() is replaced by vcpu_sys_reg().

v1 -> v2:
- this patch also is candidate for 4.9-stable
---
 virt/kvm/arm/pmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 69ccce308458..9a47b0cfb01d 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -299,6 +299,9 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
 	if (val == 0)
 		return;
 
+	if (!(vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
+		return;
+
 	enable = vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
 	for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++) {
 		if (!(val & BIT(i)))
-- 
2.20.1