linux-kernel - Re: [PATCH v4 2/2] KVM: move vcpu id checking to archs

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Message-ID: <20160422122210.50450345.cornelia.huck@de.ibm.com>
Date:	Fri, 22 Apr 2016 12:22:10 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Greg Kurz <gkurz@...ux.vnet.ibm.com>
Cc:	Radim Krčmář <rkrcmar@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>, james.hogan@...tec.com,
	mingo@...hat.com, linux-mips@...ux-mips.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	qemu-ppc@...gnu.org, Paul Mackerras <paulus@...ba.org>,
	David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH v4 2/2] KVM: move vcpu id checking to archs

On Fri, 22 Apr 2016 11:25:38 +0200
Greg Kurz <gkurz@...ux.vnet.ibm.com> wrote:

> On Thu, 21 Apr 2016 19:36:11 +0200
> Radim Krčmář <rkrcmar@...hat.com> wrote:

> > > For other architectures, it is simply KVM_MAX_VCPUS.  
> > 
> > (Other architectures would not implement the capability.)
> > 
> 
> So this would be KVM_CAP_PPC_MAX_VCPU_ID ?
> 
> > >> I think this would also clarify the connection between VCPU limit and
> > >> VCPU_ID limit.  Or is a boolean cap better?
> > >>   
> > > 
> > > Well, I'm not fan of adding a generic API to handle a corner case...  
> > 
> > I don't like it either, but I think that introducing the capability is
> > worth avoided problems.
> > 
> 
> I admit that having separate capabilities for the number of vcpus and the
> maximum vcpu id fixes the confusion once and for all.

Yes, and I think that the new max_vpcu_id cap should be generic for
that reason.