Re: [Qemu-devel] Re: [PATCH 0/3]: Add UUID command-line option

[Jamie Lokier <jamie@shareable.org>]

Anthony Liguori wrote:
> >CMOS has enough memory for UUID, but UUID is not the only thing that
> >needs to be passed to BIOS, so eventually we can run out of space there.
> >  
> 
> I'm inclined to think that on a real machine, the UUID is stored in the 
> CMOS.

I'd imagine on a real machine the UUID cannot be changed, so it can't
be stored in the CMOS.  It's probably in the BIOS somewhere.

I quick Google suggests at least some systems store it in the SMBIOS
information, which is part of the BIOS EEPROM.  It also suggested that
some Dell laptops store it in the keyboard controller!

The logical equivalent would be to directly write the UUID (and other)
information into the Bochs BIOS when loading it into the emulator.

> >For example we have a requirement to pass additional ACPI tables that
> >user may specify on command line.
> 
> What's the use-case?  I don't think this is a very good idea.

For testing guest ACPI implementations or changing their behaviour? :-)

> You can not arbitrarily extend the backdoor interface.  It's an 
> interface defined and controlled by VMware.  If you extend it, you risk 
> breaking other OSes that are assuming that interface has a different 
> meaning.

I agree, better to define a sensible interface if extensions are
desired.

Probably at least one other VM has defined such a thing, it would be
good to copy if there is one and it's extensible.

-- Jamie