Re: [Plex86-devel] Idea for running multiple OSs

[Derek Broughton]

Cam wrote:
> That's interesting - I didn't think about that. I thought that maybe
> some hardware would save it's state internally (eg. a graphics card or
> network card) in the suspend state.
>
> swsusp looks interesting but if you could do the suspending in the BIOS
> then it would be OS-neutral. I wonder how far linux BIOS goes with
> features like suspend...

That's a big topic of discussion on the ACPI developers list.  ACPI currently
does suspend-to-disk primarily using SWSUSP, but it does support suspend via
BIOS. There are significant pluses & minuses to both methods.  So much so, that
the primary ACPI developer wanted to remove the BIOS-suspend support and the
swsusp developer wanted to keep it in :-)  There really is no absolute need for
a file-system's state to be stored in the suspend partition - I'm sure that when
I suspend (hibernate) in Windows, the file-system state is flushed to the file
system, or I would have already corrupted that partition!  Swsusp could
certainly flush the file systems if it wanted.  I'm not sure why it doesn't (or
perhaps I'm just mistaken and this really isn't a problem).  I guess that's part
of the dilemma with suspend states, though. How much do you decide to suspend
temporarily and how much do you commit. With ACPI you should always be able to
decide that at the user level, so I can have a script that will permanently save
what I need (e.g., umount the FAT32 partition and eject a PCMCIA card that
doesn't suspend properly), _then_ invoke swsusp to save everything else as fast
as possible.

> Presumably vmware or plex86 wouldn't be able to share filesystems
> either, unless there is something clever going on at a high level (eg.
> present the filesystem as a networked one, or as a removable one). Once
> you know of the limitations it should be a minor problem to work around.

Absolutely.

> I just thought it would be neat to run at full speed and switch OSs
> without rebooting. It's a simple solution to a simple problem, instead
> of a complex expensive (and elegant) solution. A lot of the reasons for
> running non linux OSs are to access multimedia stuff and games that are
> not easily available for linux.

Yeah, I think it's a pretty good solution really, though I wonder if it would be
much easier than manually doing the suspend process.  As it is now, when I use
windows I never log out, I hibernate (in fact, I usually just close the cover to
start the hibernation). Then push the power button again and start linux.  I
haven't got swsusp working, so I don't suspend linux on exit, but if I had that
the only difference between your solution and what's currently possible would be
that the shutdown process should go into 'restart' mode instead of 'power-off'.
And note that if you use a BIOS to do the suspend, you _must_ have a separate
BIOS for every OS, or your BIOS is going to only use a single suspend partition!

derek