Re: Virtual Machines, JVM in kernel, hot-swapped kernel

WCOEKAER.US.ORACLE.COM (WCOEKAER@us.oracle.com)
24 Aug 98 10:06:21 -0700

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A VM in the kernel, or a system level VM to share objects and what not is
good
in an environment where you know tons of people are running the same code.
Otherwise it would just trash your environment. For companies running all
their apps in java that would be good, for a generic system where you have
random users I don't see why you would go through all the trouble.

if you really want to tightly integrate a vm and have sharing of objects,
one
way could be to have some sort of a generic cache for a VM, and then have
session level or userlevel spaces where you store local stuff, and you would
do your GC in on the userspace and not on the shared object cache (just use
LRU there). Again, this would really work well in the specific type of
usage...

and like hpa said, then there is the security problem :) which would be a
REAL
mess in such a case, you will have to play around with, who can invoke this
object, how do you keep track of that and all... you really want to go there
?

Wim.

The statements and opinions expressed here are my own and
do not necessarily represent those of Oracle Corporation.

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Date: 24 Aug 98 04:26:46
From:hpa@transmeta.com (H. Peter Anvin)
To:linux-kernel@vger.rutgers.edu
Subject:Re: Virtual Machines, JVM in kernel, hot-swapped kernel
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Followup to: <19980822152913.18494@lucifer.guardian.no>
By author: Alexander Kjeldaas <astor@guardian.no>
In newsgroup: linux.dev.kernel
>
> You don't want a VM in the kernel, but you might want a system level
> VM - a single VM used by all java-programs what will do caching and
> optimalization etc. Other than that, it is interesting to see if
> there are any new services needed by a VM that the kernel should
> provide. I know of one such service: user-level exceptions. Being
> able to handle a memory protection exception without the
> user->kernel->user context switches makes certain GC/VM-tricks much
> less expensive.
>

Hmm... I don't know if you can do that and still maintain OS
security; anyone remember the "sliding password" security hole?

-hpa

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