On Tuesday, 03/28/2006 at 12:53 EST, "Hughes, Jim - OIT" 
<[EMAIL PROTECTED]> wrote:
> I'd like to hear technical reasons why it's a bad idea to run ZVM under
> ZVM in production or why it's a good idea. Business reasons pro and con
> are welcome as well.

The most technical reason I can think of: Performance degradation due to 
the lack of SIE support for the 2nd level guest.  The 3rd level guests 
will run, but dog slow.

Another technical reason:  Again, because of the lack of SIE support, 
z/VM's security certification (ISO/IEC 15408, Common Criteria) does not 
apply to 2nd level VM systems.

The lack of SIE support means that when the second level CP issues a SIE 
instruction, the second level CP will itself exit from SIE and the first 
level CP must construct a SIE instruction to quasi-simulate the SIE issued 
by the guest.

Alan Altmark
z/VM Development
IBM Endicott

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