Re: Bug#584846: Detects only 64MB and fails to boot on Intel GreenCity board if e820 hooked by GRUB2

From: H. Peter Anvin
Date: Sat Jun 12 2010 - 20:16:49 EST

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.


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

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