That is the sort of thing I was thinking of. I don't pretend to be a VM 
expert.. 

Charles


-----Original Message-----
From: IBM Mainframe Assembler List [mailto:[email protected]] On 
Behalf Of Gary Weinhold
Sent: Thursday, March 28, 2019 1:54 PM
To: [email protected]
Subject: Re: Determing the Presence of an Instruction

This is probably part of Start Interpretive Execution (assuming that's 
still used).  VM used to be based on running users in problem state so 
every privop is intercepted , but SIE allows more selective trapping of 
which ops are intercepted especially for operating systems like z/OS.  I 
think VM was trapping STCK during the Y2K testing era as an example of 
non-privileged ops.

On 2019-03-28 4:42 p.m., Charles Mills wrote:
> Is this one of those situations that is controlled by a control register bit? 
> VM does not interpret every instruction like Hercules. It must be getting an 
> interrupt on STFLE or whatever.
>
> Charles
>
>
> 

Gary Weinhold 
Senior Application Architect 

DATAKINETICS | Data Performance & Optimization 

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-----Original Message-----
> From: IBM Mainframe Assembler List [mailto:[email protected]] 
> On Behalf Of Tom Marchant
> Sent: Thursday, March 28, 2019 11:48 AM
> To: [email protected]
> Subject: Re: Determing the Presence of an Instruction
>
> On Thu, 28 Mar 2019 09:56:23 -0700, Charles Mills wrote:
>
>> VM does a fair amount of "interception" and instruction simulation in any 
>> event.
> For privileged instructions, yes. In this case, something has to happen for 
> non-privileged instructions too.
>

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