Subject: Re: [PATCH v2 35/45] KVM: s390: Manually invoke vcpu setup during kvm_arch_vcpu_create()

From: Sean Christopherson <[email-masked]>
Date: Fri, 20 Dec 2019 07:56:07 -0800

On Fri, Dec 20, 2019 at 11:04:45AM +0100, Cornelia Huck wrote:
> On Wed, 18 Dec 2019 13:55:20 -0800
> Sean Christopherson <[email-masked]> wrote:
> 
> > Rename kvm_arch_vcpu_setup() to kvm_s390_vcpu_setup() and manually call
> > the new function during kvm_arch_vcpu_create().  Define an empty
> > kvm_arch_vcpu_setup() as it's still required for compilation.  This
> > is effectively a nop as kvm_arch_vcpu_create() and kvm_arch_vcpu_setup()
> > are called back-to-back by common KVM code.  Obsoleting
> > kvm_arch_vcpu_setup() paves the way for its removal.
> > 
> > Note, gmap_remove() is now called if setup fails, as s390 was previously
> > freeing it via kvm_arch_vcpu_destroy(), which is called by common KVM
> > code if kvm_arch_vcpu_setup() fails.
> 
> Yes, this looks like the only thing that needs to be undone
> (sca_add_vcpu() is done later in the process.)
> 
> Maybe mention that gmap_remove() is for ucontrol only? I was confused
> for a moment :)

Will do.

Would it also make sense to open code __kvm_ucontrol_vcpu_init() in a
separate patch immediately preceding this change?  That'd make it a little
more obvious why gmap_remove() is called, and it would eliminate the
"uninit" verbiage in the label, e.g.:

        if (kvm_is_ucontrol(vcpu->kvm)) {
                vcpu->arch.gmap = gmap_create(current->mm, -1UL);
                if (!vcpu->arch.gmap) {
                        rc = -ENOMEM;
                        goto out_free_sie_block;
                }
                vcpu->arch.gmap->private = vcpu->kvm;
        }

        VM_EVENT(kvm, 3, "create cpu %d at 0x%pK, sie block at 0x%pK", id, vcpu,
                 vcpu->arch.sie_block);
        trace_kvm_s390_create_vcpu(id, vcpu, vcpu->arch.sie_block);

        rc = kvm_s390_vcpu_setup(vcpu);
        if (rc)
                goto out_free_ucontrol_gmap;
        return 0;

out_free_ucontrol_gmap:
        if (kvm_is_ucontrol(vcpu->kvm))
                gmap_remove(vcpu->arch.gmap);
out_free_sie_block:
        free_page((unsigned long)(vcpu->arch.sie_block));
        return rc;
}

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