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

Jan Beulich
Tue, 12 Nov 2013 12:30:52 -0000

>>> On 12.11.13 at 13:11, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> Ian Campbell <Ian.Campbell@citrix.com> wrote:
>>As it stands for HVM guests the e820 map is determined by hvmloader, so
>>it makes sense for it to populate standard CMOS locations with the
>>values they should have.
>
> CMOS has memory values? That is standard PC spec? Yikes!

That''s the first time I hear about this - there are a couple of more
or less standard locations in CMOS where some of the memory
gets reported, but all are at most two bytes wide and (having at
best 64k granularity) don''t allow expressing memory beyond 4Gb.

Now, if there is a standard for the locations used here, fine with
me (but it should be referenced in the commit message then). But
if this is custom, then I wonder (a) how compatible such an
extension is going to be and (b) why it needs to be restricted to
3 bytes (allowing to cover only up to 1Tb).

Jan