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Date: Thu, 19 Apr 2007 14:11:40 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Andi Kleen <ak@suse.de>
CC: Chuck Ebbert <cebbert@redhat.com>, Jeremy Fitzhardinge <jeremy@goop.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       virtualization@lists.osdl.org, lkml <linux-kernel@vger.kernel.org>,
       Zachary Amsden <zach@vmware.com>, Chris Wright <chrisw@sous-sol.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 10/28] i386: map enough initial memory to create lowmem
 mappings
References: <20070414204154.871250608@goop.org> <200704192250.52633.ak@suse.de> <4627D756.5020405@zytor.com> <200704192304.01053.ak@suse.de>
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Andi Kleen wrote:
> On Thursday 19 April 2007 22:55:50 H. Peter Anvin wrote:
>> Andi Kleen wrote:
>>>> Is some version of this going in for 2.6.21, or is it not a real problem?
>>> When it's only seen with Xen it's not a real problem right now.
>> It's not just seen only with Xen, though.  It will affect all kernels in 
>> a particular range of sizes, and we have ordinary kernels covering that 
>> range (in fact, Xen hardly affects size in that way.)
> 
> Then we would have seen reports surely?

The critical size window is relatively small, though.  The size of the 
uncompressed kernel mod 4 MB must be above 3.75 MB or so.  If you have 
less than 1 GB RAM, the window is even smaller.  This is strictly 
configuration-dependent, and has nothing to do with Xen.  It just so 
happened that the first people to detect and diagnose it (as opposed to 
just "it doesn't boot") were Xen people.

	-hpa