Thanks!

Charles

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of Ed Jaffe
Sent: Wednesday, December 14, 2016 10:00 AM
To: [email protected]
Subject: Re: Question on SPKA and Control Register 3

On 12/14/2016 8:47 AM, Charles Mills wrote:
> Interesting. I have avoided going there, but perhaps I should.

The code (originally developed many, many years ago) builds and saves a model 
left-half PSW at initialization time, thus allowing the actual switch back to 
problem state and TCB key to be done with minimal overhead:

      PUSH  USING                  <Save USING status
      USING PSW,work_field         <Synchronize PSW DSECT
      L     R14,MODELPSW            Load model PSW - (First half)
      LARL  R15,CONTINUE            PSW instruction address
      OILH  R15,X'8000'             ..it's AMODE(31)
      STM   R14,R15,PSW             Build the PSW
      STOSM PSWMASK,0               Retain the current system mask
      MVZ   PSWBYTE1,TSOPKF         Set Key
      OI    PSWBYTE1,PSWPROB        Problem state
      LPSW  PSW                     Switch to TCB key and prob state
      POP   USING                  <Restore USING status
CONTINUE   DC 0H

Obviously, this will need to be looked at if we ever move it above the bar...

--
Edward E Jaffe
Phoenix Software International, Inc
831 Parkview Drive North
El Segundo, CA 90245
http://www.phoenixsoftware.com/

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