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Date: Wed, 19 Oct 2011 10:05:25 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Ian Campbell <ijc@hellion.org.uk>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>,
        Jeremy Fitzhardinge <jeremy@goop.org>, xen-devel@lists.xensource.com,
        linux-kernel@vger.kernel.org, Maxim Uvarov <maxim.uvarov@oracle.com>
Subject: Re: [Xen-devel] Re: [PATCH] XEN_DOMAIN_MEMORY options.
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On Sat, Oct 15, 2011 at 05:42:48PM +0100, Ian Campbell wrote:
> On Sat, 2011-10-15 at 09:05 -0400, Konrad Rzeszutek Wilk wrote:
> > > On 10/14/2011 04:41 PM, Jeremy Fitzhardinge wrote:
> 
> > > >While it would be very silly to put 128GB of actual RAM on a 32-bit
> > > >machine, systems can have non-contiguous RAM placed at high addresses,
> > > >which would no longer be accessible.
> > 
> > Do you have some ideas of which machines that might be?
> 
> Even if you were on such a machine, the discontiguity
> (discontiguousness?) wouldn't ever be reflected in the pseudo-physical
> memory map, would it? So since this variable controls the maximum size
> of the p2m (rather than the m2p) it doesn't need to be larger than the
> maximum sane 32 bit guest size (<64G).

I think it is the other way around. The M2P would not be affected but
the P2M might? The "discontinuity" is in the E820 right? (so mega big
holes in it).