On 19 August 2014 05:45, Binyamin Dissen <[email protected]> wrote: > :>But what would be the best way to determine whether the caller had entered > :>in Supervisor State so I could return to the caller in his original mode > :>(and also avoid the overhead of MODESET)? Some sort of "store PSW" > :>instruction so I could TM on bit 15? > > Look at the EPSW instruction.
EPSW is interesting because it didn't (and logically couldn't) exist until the Interpretive Execution facility came along. An unprivileged instruction that revealed details of the true current PSW when running under VM/370 would break the rule that it's not possible to determine if you are running in a VM, other than by observing artifacts like execution speed, or by using a non architected facility like Diagnose. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
