linux-kernel - Re: [PATCH 10/28] i386: map enough initial memory to create lowmem mappings

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Message-ID: <4627DDAD.4070805@redhat.com>
Date:	Thu, 19 Apr 2007 17:22:53 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Andi Kleen <ak@...e.de>, Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zach@...are.com>,
	Chris Wright <chrisw@...s-sol.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 10/28] i386: map enough initial memory to create lowmem
 mappings

H. Peter Anvin wrote:
> 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.

I never saw a description of the symptoms of encountering this bug.
Does it just hang, or what?

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