linux-kernel - Re: Bug#584846: Detects only 64MB and fails to boot on Intel Green City board if e820 hooked by GRUB2

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Message-ID: <4C14235B.7030605@zytor.com>
Date:	Sat, 12 Jun 2010 17:16:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Josh Triplett <josh@...htriplett.org>
CC:	Ben Hutchings <ben@...adent.org.uk>, x86@...nel.org,
	584846@...s.debian.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Bug#584846: Detects only 64MB and fails to boot on Intel Green
 City board if e820 hooked by GRUB2

On 06/12/2010 05:07 PM, Josh Triplett wrote:
> On Sat, Jun 12, 2010 at 04:02:44PM -0700, H. Peter Anvin wrote:
>> On 06/12/2010 03:26 PM, Josh Triplett wrote:
>>>
>>> Everything looks identical except for the region GRUB hooked right below
>>> the first reserved region; the unhooked version has available memory
>>> from 0-0x9cbf0, and the hooked version has available memory from
>>> 0-0x9cba0, then reserved from 0x9cba0-0x9cbec, then 4 bytes of available
>>> memory, and then the same reserved region as before.
>>
>> Actually... are both these done by chainloading Grub (with and without
>> mapping), or is the unhooked done without chainloading Grub at all?
>>
>> To me it looks like something is chaining INT 15h even in the
>> "unchained" case...
> 
> The "unhooked" case still chainloaded from GRUB, just without calling
> drivemap and thus without hooking anything.  I can test without
> chainloading from GRUB, though to the best of my knowledge GRUB doesn't
> hook int 15 unless it needs to intercept e820 (and e801 and 88).
> 
> - Josh Triplett

Well *something* is... and it might not be Grub but one of the expansion
ROMs.  If so, the problem is probably Grub stepping on the expansion ROM
by not honoring FBM.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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