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RE: [Xen-devel] Xen PXE solution

  • To: <aball@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Ben Thomas" <bthomas@xxxxxxxxxxxxxxx>
  • Date: Mon, 16 Oct 2006 15:47:21 -0400
  • Delivery-date: Mon, 16 Oct 2006 12:44:50 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcbxWdRPmY1mGVcCT12N6VpzRj6cxQAAM/Sm
  • Thread-topic: [Xen-devel] Xen PXE solution

Hi Andrew,

I added the address logging to check out a few questions I had.
The use of 0C0000 is interesting, but as you note, it's safe as
it's used as a scratch area before it's filled in with the
vga bios.

My main concern is with the use of memory below 0A0000.  I'm
chasing a problem in an OS, and it sure looks like a problem
I submitted a fix for (to the OS, not this project) about a
year back. It was related to too little free memory in the
first 1MB. Hence, my interest in the layout, especially the
use of memory below 0A0000. It's likely that my suspicions are
incorrect, but curiousity usually wins.

Anyhow, I saw your note and thought I'd pass on what little I
had about it.


-----Original Message-----
From: Andrew D. Ball [mailto:aball@xxxxxxxxxx]
Sent: Mon 10/16/2006 3:33 PM
To: Ben Thomas; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Xen PXE solution

On Mon, 2006-10-16 at 13:46 -0400, Ben Thomas wrote:
>         The most important work to be done that I can think of before
>         this can
>         work is to clearly document which parts of memory are occupied
>         by
>         what firmware for HVM domU's and proceed with troubleshooting
>         the
>         memory corruption.

> Is this along the lines of what you are looking for ?

Sure is!  Didn't know this was logged -- it's been awhile since I worked
on this part.

I think it would be useful to document this layout somewhere, probably
on the wiki.  I saw an SMBIOS fix that scared me, because it used
0xc0000 as a scrap area.  Shouldn't hurt anything, since the VGA BIOS is
loaded after the SMBIOS tables, but scares me nonetheless because I
don't know of any documentation for the HVM virtual firmware other than
the code and the logs.


> (XEN) (GUEST: 6) HVM Loader
> (XEN) (GUEST: 6) Detected Xen v3.0-unstable
> (XEN) (GUEST: 6) Writing SMBIOS tables [0009f000 - 0009f140] ...
> (XEN) (GUEST: 6) Loading ROMBIOS [000f0000 - 00100000] ...
> (XEN) (GUEST: 6) Creating MP tables ...
> (XEN) (GUEST: 6) Loading Cirrus VGABIOS [000c0000 - 000c8000] ...
> (XEN) (GUEST: 6) Loading ACPI [000ea000 - 000eb000] ...
> (XEN) (GUEST: 6) Loading VMXAssist [000d0000 - 000d5200] ...
> (XEN) (GUEST: 6) VMX go ...
> I have some questions/concerns about the layout of memory, which is
> why I have this info.
> -b

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