From: Mike Larkin <mlarkin@nested.page>
Subject: Re: vmd(8): Use 32-bit direct kernel launch for both amd64 and i386
To: Theo de Raadt <deraadt@openbsd.org>
Cc: Mark Kettenis <mark.kettenis@xs4all.nl>, Hans-Jörg Höxer <hshoexer@genua.de>, tech@openbsd.org
Date: Wed, 20 Aug 2025 12:13:55 -0700

On Wed, Aug 20, 2025 at 08:52:40AM -0600, Theo de Raadt wrote:
> > This strategy seems to work quite well, and I think it would be nice
> > if in the future amd64 would use the same model.
>
> With the legacy bootloader, I think it is difficult to allocate memory
> correctly, and then furthermore --  place code high if that is the
> decided location.

Yeah. I think the legacy bootloader will just remain as is. The clobbering
of "special" phys ranges seems to only have been reported on EFI machines,
anyway (not saying it's impossible with legacy boot though, only that I
haven't seen it reported).

>
> Anyways, the goal is to avoid the PA overlapping some weird object
> in the address space on weird machines.  There's no security benefit
> from being at such a PA.
>