|| ||Linus Torvalds <torvalds-AT-linux-foundation.org>|
|| ||"Miller, Marc" <marc.miller-AT-amd.com>|
|| ||Re: Drivers -- below the OS?|
|| ||Fri, 3 Aug 2007 18:12:57 -0700 (PDT)|
On Fri, 3 Aug 2007, Miller, Marc wrote:
> I recently came across an article claiming that virtualization "liberates"
> the OS from the hardware, basically implying that the hypervisor can now
> contain all of the drivers and that the OS just needs to have a standard
> abstraction layer for accessing the true driver involved.
I think what you're seeing is virtualization proponents being absolutely
_desperate_ for any reason to use virtualization.
The fact is, the absolute last place you want to see drivers is in the
hypervisor, not only because the added abstraction layer is inevitably a
big performance problem, but because hardware and drivers are by
definition buggier than "generic" code that can be tested.
I expect hardware and drivers to reach the same kind of stability we have
in generic code the moment people no longer develop hardware actively. At
that point, drivers probably become stable too, and can be put in the
hypervisor. Any time before that happens, you want the drivers "further
out", rather than "closer in" to the system.
So next time you hear about hypervisors doing anything at all, ask
yourself where the message comes from. Does it come from a group of people
who are desperately trying to make themselves appear relevant? Or does it
come from forty years of actual real-life practice?
[ Side note: I don't doubt at all that virtualization is useful in some
areas. What I doubt rather strongly is that it will ever have the kind
of impact that the people invovled in virtualization want it to have. It
would appear that virtualization is the "message-passing microkernel" of
this decade, and that people have a really hard time accepting that the
reason operating systems still basically look 100% the same today as
they did almost forty years ago, is that that is simply a very practical
So every decade, you'll find somebody who "reinvents" the OS. Apparently
just because they are bored with the fact that operating systems have
really been the same-old, same-old for a long time.
Guess what? Wheels have been round for a really long time, and anybody
who "reinvents" the new wheel is generally considered a crackpot. It
turns out that "round" is simply a good form for a wheel to have. It may
be boring, but it just tends to roll better than a square, and "hipness"
has nothing what-so-ever to do with it ]
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