arm/arm64: kvm: pmu: Make overflow handler NMI safe

hulk inclusion
category: feature
bugzilla: 12804
CVE: NA

-------------------------------------------------

When using an NMI for the PMU interrupt, taking any lock migh cause a
deadlock. The current PMU overflow handler in KVM takes takes locks when
trying to wake up a vcpu.

When overflow handler is called by an NMI, defer the vcpu waking in an
irq_work queue.
Signed-off-by: NJulien Thierry <julien.thierry@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/kvm/arm_pmu.h

@@ -37,6 +37,7 @@ struct kvm_pmu {
 	bool ready;
 	bool created;
 	bool irq_level;
+	struct irq_work overflow_work;
 };
 
 #define kvm_arm_pmu_v3_ready(v)		((v)->arch.pmu.ready)

virt/kvm/arm/pmu.c

@@ -273,15 +273,37 @@ void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu)
 	kvm_pmu_update_state(vcpu);
 }
 
+static inline struct kvm_vcpu *kvm_pmu_to_vcpu(struct kvm_pmu *pmu)
+{
+	struct kvm_vcpu_arch *vcpu_arch;
+
+	vcpu_arch = container_of(pmu, struct kvm_vcpu_arch, pmu);
+	return container_of(vcpu_arch, struct kvm_vcpu, arch);
+}
+
 static inline struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu;
-	struct kvm_vcpu_arch *vcpu_arch;
 
 	pmc -= pmc->idx;
 	pmu = container_of(pmc, struct kvm_pmu, pmc[0]);
-	vcpu_arch = container_of(pmu, struct kvm_vcpu_arch, pmu);
-	return container_of(vcpu_arch, struct kvm_vcpu, arch);
+	return kvm_pmu_to_vcpu(pmu);
+}
+
+/**
+ * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding
+ * to the even.
+ * This is why we need a callback to do it once outside of the NMI context.
+ */
+static void kvm_pmu_perf_overflow_notify_vcpu(struct irq_work *work)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_pmu *pmu;
+
+	pmu = container_of(work, struct kvm_pmu, overflow_work);
+	vcpu = kvm_pmu_to_vcpu(pmu);
+
+	kvm_vcpu_kick(vcpu);
 }
 
 /**
@@ -299,7 +321,11 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
 
 	if (kvm_pmu_overflow_status(vcpu)) {
 		kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
-		kvm_vcpu_kick(vcpu);
+
+		if (!in_nmi())
+			kvm_vcpu_kick(vcpu);
+		else
+			irq_work_queue(&vcpu->arch.pmu.overflow_work);
 	}
 }
 
@@ -501,6 +527,9 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
 			return ret;
 	}
 
+	init_irq_work(&vcpu->arch.pmu.overflow_work,
+		      kvm_pmu_perf_overflow_notify_vcpu);
+
 	vcpu->arch.pmu.created = true;
 	return 0;
 }