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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 20 Apr 2022 20:25:19 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     Pierre Morel <pmorel@...ux.ibm.com>, 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, 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

On Wed, Apr 20, 2022 at 03:22:41PM +0200, Claudio Imbrenda wrote:
> On Wed, 20 Apr 2022 14:05:00 +0200
> Heiko Carstens <hca@...ux.ibm.com> wrote:
> 
> > > +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;  
> 
> so if the CPU moved to a different socket, it's not a change?
> and if nothing happened, it is a change?

How do you translate the above code to your statement?