[U-Boot] [PATCH 5/7] disk: Allow alternate EFI partition signature

Stefan Reinauer
2012-10-15T17:17:22Z

On Mon, Oct 15, 2012 at 8:19 AM, Stephen Warren <swarren@wwwdotorg.org>wrote:

> On 10/12/2012 06:26 PM, Simon Glass wrote:
> > From: Stefan Reinauer <reinauer@chromium.org>
> >
> > ChromeOS uses a GPT partition table to partition the disk.
> > However, Windows will refuse to install on a GPT partitioned
> > disk if there is no EFI available (Even if there is an MBR, too)
> > To hide the GPT partition table from Windows, we need to write
> > it with a header magic other than "EFI PART". To support old
> > and new systems, Check for the magic string "CHROMEOS" too.
>
> Surely if you wanted to install Windows on a disk containing ChromeOS,
> you would just wipe the disk and re-partition it? I suppose perhaps
> you're talking about dual-boot though?
>

Yes, this is only required if we're dual-booting on Windows and ChromeOS on
the same disk.

Either way, it doesn't see like a good idea to be using non-standard EFI
> signatures - especially if the idea is to hide the GPT from Windows, and
> presumably then have Windows use the MBR partitions, since that will end
> up with a decidedly non-standard partition setup; some partitions will
> only be represented in the MBR (those Windows creates) and some in GPT
> (presumably whatever ChromeOS created before).
>

Yes, you will have to create a hybrid partition setup to make this work. It
is unfortunate that Windows enforces this and there is no real way around
it.
This is a workaround specific to ChromeOS machines, and should be fixed
differently in the long run (e.g. by using Tiano Core as a payload instead
of SeaBIOS for booting Windows)

Stefan