Re: Machine or O/S (z/os) instruction to recognize a zpdt ?

Le 5/11/2019 à 9:19 PM, Binyamin Dissen [email protected] 
[hercules-390] a écrit :
> EPSW has no privilege restriction, and should you issue it when you expect to
> be in supervisor state and you see that the PSW is not in supervisor state you
> now know that you are under some kind of VM.

Actually you won't if you are running any form of IBM VM product or PR/SM.

Under VM/XA+ (VM/ESA, z/VM) issuing a EPSW instruction (assuming the 
architecture supports it) from a virtual machine will return the version 
as seen by SIE (assuming there isn't a specific SIE intercept - haven't 
checked if EPSW can be intercepted)... So from a program point, if the 
VM PSW is in Supervisor state, the "extracted" PSW will be a supervisor 
state PSW the same as it would be on bare metal  (not the PSW that 
existed when the SIE instruction was executed by CP or the hypervisor).

EPSW doesn't exist in S/370 mode for the very reason that it breaks 
virtualisation.

EPSW only breaks virtualisation if you are using a 
hypervisor/virtualisation platform that doesn't use SIE.

--Ivan




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