[okl4-developer] Hi all, i am a student.and now i am studying os virtualization

[Antonin SUBTIL]

Hello,

Some might correct what I'll say, I dunno if i'm 100% right (or just 50%?).

Virtualisation is a wonderfull new toy for SI ;) which relies on providing
some HAL to unmodified OS so they can run on top of hypervisor just like if
it was bare metal. Then you can have plenty of OSes on the same machine as
you're not longer relying on hardware. Seems to me like the "basic idea" of
commercial virtualization :p
I recommand you to have a look on Popek and Goldberg about virtualization,
and their rules about "how virtualization should be" (most of code should
run on processor, not being emulated / should exhibit an effect identical as
if it was on bare metal / hypervisor should have a complete control of
system)

However, IA-32 (x86) has a huge problem : it's not "virtualization
compliant" (well, now, it tend to be), and then you have to watch the
execution of your virtual machine to avoid big problems. That's why
virtualization is slow.........
However (2), some guys come up with PARA-virtualization : modifying the
guest(s) OS(es) so they are "aware" of being on top of hypervisor. (That's
Xen and so on...). This idea bring better performances, "near natives" says
some, but need to change OS.
However (3), some other guys come up with PRE-virtualization : annotating
the guest(s) OS(es) at compilation time, so they can run on bare-metal and
on specific hypervisors... Yet this idea was not commercialized.

Now, to the question "how to do with dual guest os", which I understand as
"how to run 2 guest OS", I'd answer that's seems easy on OKL4 : just have to
change some configuration files, so there would be (for example) not one
OKLinux but several.
Then you might answer "and priorities?" OKLinux runs on 99 (main threads)
and 100, but can share them. I dunno about the perf then :p
I'd ask you : how do you want your two OSes to run ? Is there one RT or with
some higher priority ?  for 100% of its execution time or less?  (you can
had an OS  with higher priority, or divide it to higher and lower priority
(...))

Ok, might not be the answer you wanted :p Maybe you should have a look  into
/package/iguana/SConscruct ?  It would show you how stuff are linked inside
one image ( so how to put L4+l4test or l4+polls+oklinux ...)

2008/5/15 quanchen <westwolf2008 at gmail.com>:

>
> Hi all
>       i am a student.and now i am studying os virtualization.l4 is
> wonderful,but there is not enough information
>  about how to do with dual guest os,may i get some help at here?
>
>  Best Regards,
>  quanchen
>  2008-05-15
> --
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-- 
Antonin Subtil,
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FR-33000 Bordeaux
+33 (0)6.77.40.17.69

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