linux-kernel - [PATCH v5 01/12] KVM: arm64: PMU: Introduce a helper to set the guest's PMU

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Message-ID: <20230817003029.3073210-2-rananta@google.com>
Date:   Thu, 17 Aug 2023 00:30:18 +0000
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Oliver Upton <oliver.upton@...ux.dev>,
        Marc Zyngier <maz@...nel.org>
Cc:     Alexandru Elisei <alexandru.elisei@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Shaoqin Huang <shahuang@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v5 01/12] KVM: arm64: PMU: Introduce a helper to set the
 guest's PMU

From: Reiji Watanabe <reijiw@...gle.com>

Introduce a new helper function to set the guest's PMU
(kvm->arch.arm_pmu), and use it when the guest's PMU needs
to be set. This helper will make it easier for the following
patches to modify the relevant code.

No functional change intended.

Signed-off-by: Reiji Watanabe <reijiw@...gle.com>
Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
---
 arch/arm64/kvm/pmu-emul.c | 52 +++++++++++++++++++++++++++------------
 1 file changed, 36 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 5606509724787..0ffd1efa90c07 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -865,6 +865,32 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
 	return true;
 }
 
+static int kvm_arm_set_vm_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
+{
+	lockdep_assert_held(&kvm->arch.config_lock);
+
+	if (!arm_pmu) {
+		/*
+		 * No PMU set, get the default one.
+		 *
+		 * The observant among you will notice that the supported_cpus
+		 * mask does not get updated for the default PMU even though it
+		 * is quite possible the selected instance supports only a
+		 * subset of cores in the system. This is intentional, and
+		 * upholds the preexisting behavior on heterogeneous systems
+		 * where vCPUs can be scheduled on any core but the guest
+		 * counters could stop working.
+		 */
+		arm_pmu = kvm_pmu_probe_armpmu();
+		if (!arm_pmu)
+			return -ENODEV;
+	}
+
+	kvm->arch.arm_pmu = arm_pmu;
+
+	return 0;
+}
+
 static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
 {
 	struct kvm *kvm = vcpu->kvm;
@@ -884,9 +910,13 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
 				break;
 			}
 
-			kvm->arch.arm_pmu = arm_pmu;
+			ret = kvm_arm_set_vm_pmu(kvm, arm_pmu);
+			if (ret) {
+				WARN_ON(ret);
+				break;
+			}
+
 			cpumask_copy(kvm->arch.supported_cpus, &arm_pmu->supported_cpus);
-			ret = 0;
 			break;
 		}
 	}
@@ -908,20 +938,10 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 		return -EBUSY;
 
 	if (!kvm->arch.arm_pmu) {
-		/*
-		 * No PMU set, get the default one.
-		 *
-		 * The observant among you will notice that the supported_cpus
-		 * mask does not get updated for the default PMU even though it
-		 * is quite possible the selected instance supports only a
-		 * subset of cores in the system. This is intentional, and
-		 * upholds the preexisting behavior on heterogeneous systems
-		 * where vCPUs can be scheduled on any core but the guest
-		 * counters could stop working.
-		 */
-		kvm->arch.arm_pmu = kvm_pmu_probe_armpmu();
-		if (!kvm->arch.arm_pmu)
-			return -ENODEV;
+		int ret = kvm_arm_set_vm_pmu(kvm, NULL);
+
+		if (ret)
+			return ret;
 	}
 
 	switch (attr->attr) {
-- 
2.41.0.694.ge786442a9b-goog