linux-kernel - Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit

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Message-ID: <47C85294.9030902@zytor.com>
Date:	Fri, 29 Feb 2008 10:44:36 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
CC:	Mark McLoughlin <markmc@...hat.com>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	Ingo Molnar <mingo@...e.hu>, Ian Campbell <ijc@...lion.org.uk>,
	Andi Kleen <ak@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit

Alexander van Heukelum wrote:
> 
> My first guess is that the BIOS data area is completely non-existent for
> Xen.
> Is it guaranteed that the memory is zeroed out on boot? In that case we
> can
> special-case it easily:
> 
> change:
>         /* Paranoia: should never happen, but... */
>         if (lowmem >= 0x100000)
>                 lowmem = 0xa0000;
> 
> into:
>         /* Strange case, like Xen ;) */
>         if (lowmem == 0 || lowmem >= 0x100000)
>                 lowmem = 0x9f000;
> 
> Can you test that?
> 

The EBDA is optional anyway; I presume it should have a zero pointer if 
it isn't present.

	-hpa
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