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Re: Xen vs VMware

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Sun, 22 Oct 2006 10:11:53 -0700 (PDT)

:> Can you point out which processors have this hardware -- are they the
:> 64-bit models only?  My instincts tell me that the 64-bit hardware
:> could virtualize a 32-bit machine -- but that's a pure guess on my part.
:No, it has nothing to do with 32-bit or 64-bit.
:Amd calls it Pacifica and Intel Vanderpool or VT.
:Newer Athlon 64 (AM2), Opteron, Core 2, All Intel from Apple etc. have it.
:AFAIR the non Apple mobile Core don't have it.

    There's nothing really special about any of it.  It's just a way for
    the processor to run in ring 0 (kernel mode) but still have restricted,
    trappable access to hardware resources.  That's it.

    My personal opinion is that its a hack on top of a hack.  As much as
    it may seem like a nice idea to be able to run an operating system
    this way, I think it's an even better idea to spend the effort to
    retool the operating system to a more restrictive spec that does not
    require hardware virtualization technology to run, which is what I am

    But I expect momentum will continue to build for the hardware
    virtualization method of doing things because OS vendors traditionally
    have not cooperated on creating a common hardware abstraction layer.

    The only thing about the new virtualization technology that really
    interests me is that the MMU will operate natively under it... that is,
    there will be no need to emulate the MMU.  That is the *ONLY* part of
    the whole mess that can actually lead to significant improvements in
    performance in a hardware virtualized environment over a software
    virtualized environment.
					Matthew Dillon 

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