On 12/8/20, 5:42 PM, "Linux on 390 Port on behalf of Paul Gilmartin"
<[email protected] on behalf of [email protected]> wrote:
> On 2020-12-08, at 14:12:21, Bruce Hayden wrote:
>
> z/VM doesn't hide the hardware. In just about all cases, if it won't run
> in an LPAR, it also won't run under z/VM.
> I recall a counterexample was OpenSolaris. It wouldn't run in
> an LPAR, but only under VM. I suspect the matter was not "hid[ing]
> the hardware" but required CP services not available from the hardware.
Bruce is correct. Without ESA/390 mode support in the processor, something as
old as SLES9 won't run reliably as a VM guest. VM doesn’t simulate support
that's not in the hardware and I think you'll spend a lot of time chasing
snarks when things break unexpectedly. Probably time to just bite the bullet
and build new systems.
Reflecting on OpenSolaris, we deliberately and intentionally wrote the code to
exploit VM services because at the time we felt that LPARs were insufficiently
flexible and too difficult to manage to be cost effective, and anyone running
it probably also had VM to support Linux. Nothing to do with the hardware (we
avoided anything that depended on hardware level where we could so it would run
on the maximum number of systems); it was easier to do that way. DIAG 250 made
disk support a lot simpler, and the DIAG 2A8 networking did the job after IBM
declined to give us enough information on the OSA to write a proper driver. We
were able to exploit a lot of the prior wisdom on running operating systems
efficiently as VM guests; no point in wasting effort re-inventing the wheel
when there was an easier way right in front of us.
In retrospect, I wish OpenSolaris had taken off. It would have saved a lot of
the recent annoyance we seem to be experiencing with the changes in device
naming and bloat of the Linux environment (and dealing with the whole systemd
aberration). Solaris is a production grade Unix system that works well - ZFS
would have been a game changer at the time.
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