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

From: Dario Faggioli <dario.faggioli@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: keir@xen.org, Ian.Campbell@citrix.com, lccycc123@gmail.com,
	george.dunlap@eu.citrix.com, msw@linux.com,
	stefano.stabellini@eu.citrix.com, ian.jackson@eu.citrix.com,
	xen-devel@lists.xen.org, Elena Ufimtseva <ufimtseva@gmail.com>
Subject: Re: [PATCH RESEND v7 1/9] xen: vnuma topology and subop hypercalls
Date: Fri, 22 Aug 2014 15:54:17 +0200	[thread overview]
Message-ID: <1408715657.3725.182.camel@Solace.lan> (raw)
In-Reply-To: <53F75EF7020000780002CB7E@mail.emea.novell.com>

[-- Attachment #1.1: Type: text/plain, Size: 1676 bytes --]

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).

Regards,
Dario

-- 
<<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)

[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 181 bytes --]

[-- Attachment #2: Type: text/plain, Size: 126 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel