linux-kernel - Re: [PATCH v8 1/2] s390x: KVM: guest support for topology function

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Date:   Wed, 20 Apr 2022 14:05:00 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, borntraeger@...ibm.com,
        frankja@...ux.ibm.com, cohuck@...hat.com, david@...hat.com,
        thuth@...hat.com, imbrenda@...ux.ibm.com, gor@...ux.ibm.com,
        wintera@...ux.ibm.com, seiden@...ux.ibm.com, nrb@...ux.ibm.com
Subject: Re: [PATCH v8 1/2] s390x: KVM: guest support for topology function

> +static inline bool kvm_s390_topology_changed(struct kvm_vcpu *vcpu)
> +{
> +	if (!test_kvm_facility(vcpu->kvm, 11))
> +		return false;
> +
> +	/* A new vCPU has been hotplugged */
> +	if (vcpu->arch.prev_cpu == S390_KVM_TOPOLOGY_NEW_CPU)
> +		return true;
> +
> +	/* The real CPU backing up the vCPU moved to another socket */
> +	if (cpumask_test_cpu(vcpu->cpu,
> +			     topology_core_cpumask(vcpu->arch.prev_cpu)))
> +		return true;
> +
> +	return false;
> +}

This seems to be wrong. I'd guess that you need

	if (cpumask_test_cpu(vcpu->cpu,
			     topology_core_cpumask(vcpu->arch.prev_cpu)))
-->		return false;
-->	return true;