linux-kernel - Re: [PATCH v2 30/45] KVM: Move vcpu alloc and init invocation to common code

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Date:   Fri, 20 Dec 2019 17:00:45 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Marc Zyngier <maz@...nel.org>, James Hogan <jhogan@...nel.org>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kurz <groug@...d.org>
Subject: Re: [PATCH v2 30/45] KVM: Move vcpu alloc and init invocation to
 common code

On Fri, 20 Dec 2019 07:53:30 -0800
Sean Christopherson <sean.j.christopherson@...el.com> wrote:

> On Fri, Dec 20, 2019 at 10:33:25AM +0100, Cornelia Huck wrote:
> > On Wed, 18 Dec 2019 13:55:15 -0800
> > Sean Christopherson <sean.j.christopherson@...el.com> wrote:  
> > > +int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> > >  {
> > > -	struct kvm_vcpu *vcpu;
> > >  	struct sie_page *sie_page;
> > >  	int rc;
> > >  
> > > -	rc = -ENOMEM;
> > > -
> > > -	vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
> > > -	if (!vcpu)
> > > -		goto out;
> > > -
> > > -	rc = kvm_vcpu_init(vcpu, kvm, id);
> > > -	if (rc)
> > > -		goto out_free_cpu;
> > > -
> > > -	rc = -ENOMEM;
> > > -
> > >  	BUILD_BUG_ON(sizeof(struct sie_page) != 4096);
> > >  	sie_page = (struct sie_page *) get_zeroed_page(GFP_KERNEL);
> > >  	if (!sie_page)
> > > -		goto out_uninit_vcpu;
> > > +		return -ENOMEM;
> > >  
> > >  	vcpu->arch.sie_block = &sie_page->sie_block;
> > >  	vcpu->arch.sie_block->itdba = (unsigned long) &sie_page->itdb;
> > > @@ -3087,15 +3070,11 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
> > >  		 vcpu->arch.sie_block);
> > >  	trace_kvm_s390_create_vcpu(id, vcpu, vcpu->arch.sie_block);
> > >  
> > > -	return vcpu;
> > > +	return 0;
> > > +
> > >  out_free_sie_block:
> > >  	free_page((unsigned long)(vcpu->arch.sie_block));
> > > -out_uninit_vcpu:
> > > -	kvm_vcpu_uninit(vcpu);
> > > -out_free_cpu:
> > > -	kmem_cache_free(kvm_vcpu_cache, vcpu);
> > > -out:
> > > -	return ERR_PTR(rc);
> > > +	return rc;  
> > 
> > This is getting a bit hard to follow across the patches, but I think rc
> > is now only set for ucontrol guests. So this looks correct right now,
> > but feels a bit brittle... should we maybe init rc to 0 and always
> > return rc instead?  
> 
> Yes, but only for a few patches until kvm_s390_vcpu_setup() is introduced,
> at which point @rc is unconditionally set at the end.

Indeed; so feel free to leave this as-is.

Reviewed-by: Cornelia Huck <cohuck@...hat.com>