linux-kernel - Re: [RFC] use realmode code to reserve end-of-conventional-memory to 1MB

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Message-ID: <47C72432.3010606@zytor.com>
Date:	Thu, 28 Feb 2008 13:14:26 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ian Campbell <ijc@...lion.org.uk>
CC:	Alexander van Heukelum <heukelum@...lshack.com>,
	Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Andi Kleen <ak@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mark McLoughlin <markmc@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] use realmode code to reserve end-of-conventional-memory
 to 1MB

Ian Campbell wrote:
> On Thu, 2008-02-28 at 14:28 +0100, Alexander van Heukelum wrote:
>> Instead of using early reservations inside the kernel code,
>> we could use the realmode code to modify the e820 memmap.
>> This patch shows what that would look like. I have not looked
>> at the case where the BIOS does not provide an e820 memmap
>> yet. Probably a full solution would need to create a fake
>> e820 memmap in that case.
> 
> An e820 is already faked up in machine_specific_memory_setup() if one
> doesn't already exist.
> 
>> Comments?
> 
> This won't work for Xen since the real-mode code never runs there. I
> think it could be fixed in xen_memory_setup() though if native goes down
> this route.
> 

s/could/should/.

You need to set up your memory map more sensibly; it's not just the 
kernel, user space tries to access these areas too.

	-hpa
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