From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH 00 of 36] x86/paravirt: groundwork for
	64-bit Xen support
Date: Wed, 25 Jun 2008 13:03:58 -0700
Message-ID: <4862A4AE.2060704@goop.org>
References: <patchbomb.1214367536@localhost> <87skv1r8ln.fsf@basil.nowhere.org>
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To: Andi Kleen <andi@firstfloor.org>
Cc: Mark McLoughlin <markmc@redhat.com>, xen-devel <xen-devel@lists.xensource.com>, Eduardo Habkost <ehabkost@redhat.com>, LKML <linux-kernel@vger.kernel.org>, Stephen Tweedie <sct@redhat.com>
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Andi Kleen wrote:
> Jeremy Fitzhardinge <jeremy@goop.org> writes:
>   
>> This moves __PAGE_OFFSET up by 16 GDT slots, from 0xffff810000000000
>>     
>
> GDT?  PDP?
>   

I meant PGD slots.  Or PML4 in x86 terms.

>> to 0xffff880000000000.  I have no general justification for this: th
>>     
>
> This will significantly decrease the maximum amount of physical
> memory supported by Linux longer term.
>   

A bit, but not "significantly".  We'd already discussed that if the 
amount of physical starts approaching 2^48 then we'd hope that the chips 
will grow some more virtual bits.

    J