[Info-vax] x86-64 XSAVE not available in Oracle VirtualBox when Microsoft Hyper-V is Enabled

[gah4]

On Monday, October 25, 2021 at 4:02:02 AM UTC-7, geze... at rlgsc.com wrote:

(snip)

> This would seem to be more of an oversight than an inherent problem. 
> As an industry, how to deal with this has been understood before the advent
> of IBM's VM/360, in the 1960's. When I started system programming OS/360
> and HASP in the mid-1970s, sharing hardware feature between physical
> devices and simulated devices was well understood, the example being
> the HASP print, punch, and read pseudo devices. 

At least for VM/370 (and its predecessor CP/67, and successors), I always
thought IBM was lucky.  One important feature of virtualization is that it
should not be possible, other than official ways (such as checking the
serial number), that one is virtualized.

It seems that the Motorola 68020 lets user programs read the bit that
indicates supervisor mode.  

The only problem that VM/370 has, is that it can't emulate STCK, such that
the virtual machine has a different TOD clock.  That mostly was a problem
testing Y2K fixes.  I am not sure if that was changed later, or not.

Then S/370 added SIE, to speed up virtualization.  From the beginning,
though, VM/370 was designed to be able to nest, such that one can test
new versions running under itself.  (Though it might get slower.)

Otherwise, Hyper-V and Virtual Box should be designed to run under,
or over, each other, though possibly slower if the speed-ups can't
be used.