Re: [PATCH] hvmloader: write extra memory in CMOS

Wei Liu
Tue, 12 Nov 2013 14:17:44 -0000

On Tue, Nov 12, 2013 at 02:13:26PM +0000, Jan Beulich
wrote:
> >>> On 12.11.13 at 15:00, Wei Liu <wei.liu2@citrix.com>
wrote:
> > On Tue, Nov 12, 2013 at 01:56:02PM +0000, Jan Beulich wrote:
> >> >>> On 12.11.13 at 14:39, Wei Liu
<wei.liu2@citrix.com> wrote:
> >> > On Tue, Nov 12, 2013 at 01:21:36PM +0000, Jan Beulich wrote:
> >> >> >>> On 12.11.13 at 13:37, Wei Liu
<wei.liu2@citrix.com> wrote:
> >> >> > However in some CMOS maps I found those bytes are
marked as reserved.
> >> >>
> >> >> Exactly. The question is whether some _other_ BIOSes then
use
> >> >> these register for other purposes...
> >> >>
> >> >
> >> > So I think now the solution is to make this code OVMF only,
are you fine
> >> > with this?
> >>
> >> Yes, provided you widen the location to at least 4 bytes.
> >>
> >
> > I''m afraid I cannot widen the location (not for technical
reason). It''s
> > a conventional protocol used by these non traditional BIOSes. It
doesn''t
> > make sense to change Xen only, right?
>
> Maybe, maybe not. But those other BIOSes must have some
> understanding of how to support >1Tb systems?
>

Presumably yes. But that''s another topic.

My point is widening this field to 4 bytes would not make them support
more than 1TB of RAM, at least not in canonical way.

Wei.

> Jan