Commit 95e92e45 authored by Julien Thierry's avatar Julien Thierry Committed by Will Deacon
Browse files

KVM: arm64: pmu: Make overflow handler NMI safe 



kvm_vcpu_kick() is not NMI safe. When the overflow handler is called from
NMI context, defer waking the vcpu to an irq_work queue.

A vcpu can be freed while it's not running by kvm_destroy_vm(). Prevent
running the irq_work for a non-existent vcpu by calling irq_work_sync() on
the PMU destroy path.

[Alexandru E.: Added irq_work_sync()]

Signed-off-by: default avatarJulien Thierry <julien.thierry@arm.com>
Signed-off-by: default avatarAlexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Sumit Garg <sumit.garg@linaro.org> (Developerbox)
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Pouloze <suzuki.poulose@arm.com>
Cc: kvm@vger.kernel.org
Cc: kvmarm@lists.cs.columbia.edu
Link: https://lore.kernel.org/r/20200924110706.254996-6-alexandru.elisei@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 05ab7281

arch/arm64/kvm/pmu-emul.c

+25 −1
Original line number Diff line number Diff line
@@ -269,6 +269,7 @@ void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu) 


	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)

		kvm_pmu_release_perf_event(&pmu->pmc[i]);

	irq_work_sync(&vcpu->arch.pmu.overflow_work);

}



u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
@@ -433,6 +434,22 @@ void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu) 
	kvm_pmu_update_state(vcpu);

}



/**

 * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding

 * to the event.

 * 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_pmc_to_vcpu(pmu->pmc);



	kvm_vcpu_kick(vcpu);

}



/**

 * When the perf event overflows, set the overflow status and inform the vcpu.

 */
@@ -465,7 +482,11 @@ 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);



		if (!in_nmi())

			kvm_vcpu_kick(vcpu);

		else

			irq_work_queue(&vcpu->arch.pmu.overflow_work);

	}



	cpu_pmu->pmu.start(perf_event, PERF_EF_RELOAD);
@@ -764,6 +785,9 @@ 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;

}

include/kvm/arm_pmu.h

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 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)

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