> > This effectively also rules out > > the possibility of any z/VM on a z14 or later being able to provide > > ESA/390 support to any Virtual Machine as well, since there many > > significant differences (register sizes, prefix area, privileged > > instructions behavior, etc) when running z/Architecture mode, and with > > CP's in that mode the only way to achieve ESA/390 behavior when the > > hardware no longer supports it would be grossly inefficient emulation. > > Why do you think that SIE would not continue to provide virtual > ESA/390 support? Today, when z/VM is running in zArch mode on the > metal on e.g. a z12, it can surely have an ESA/390 mode guest OS. I > see no reason that wouldn't continue just because the host processor > doesn't IPL in ESA/390 mode. Well, for one thing, there won't be any ESA/390 mode Dynamic Address Translation, either at SIE Guest 1 (in an LPAR) or at Guest 2 (under VM). So you certainly will not be able to run any operating system that uses ESA/390 virtual addressing, even under VM. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY
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