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Re: [Xen-devel] [PATCH RESEND v7 1/9] xen: vnuma topology and subop hypercalls

On ven, 2014-08-22 at 14:17 +0100, Jan Beulich wrote:

> > +    if ( ret )
> > +        return ret;
> > +
> > +    ret = -EFAULT;
> > +
> > +    if ( copy_from_guest(v->vdistance, u_vnuma->vdistance,
> > +                         nr_vnodes * nr_vnodes) )
> > +        goto vnuma_fail;
> > +
> > +    if ( copy_from_guest(v->vmemrange, u_vnuma->vmemrange, nr_vnodes) )
> > +        goto vnuma_fail;
> Isn't a single memory range per vnode rather limiting? Physical
> machines frequently have at least one node with two ranges to
> accommodate the hole below 4Gb. And since the interface is for
> all guest kinds I'm afraid this will harm setting up guests rather
> sooner than later. (I'm sorry for thinking of this only now.)
This actually was one concern of mine too, during the early stage of
Elena's work. I clearly remember wondering, and even asking, considering
that Linux uses more ranges per node, why using only one was ok for us.

Unfortunately, I OTOH forgot how that discussion ended and how we got to
this point, without me or anyone else (continuing to) complaining... So,
sorry from me too. :-(

Let's see what Elena and others think and, after that, how big of a
piece of work is to introduce support for more than one ranges (or
re-introduce, as I also think I remember this to be some kind of list,
during early versions of the series).


<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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