Hi Clemens,
On 24.01.2017 08:35, Clemens A. Schulz wrote:
Hi,
I just asked myself for what exactly VT-x is a hard dependency in
VirtualBox to run 64bit guests. This dependency does not exist for 32bit
guests - plus with latest Windows 10 Updates there no way to obtain VT-x
access without deactivating HyperV functionality on OS-Level.
VT-x is also a hard dependency for SMP guests (i.e. having more than one
CPU for the VM).
32-bit guests with single CPU work with software emulation, which is
significantly less accurate than hardware emulation. Extending this to
cover SMP and 64-bit (and improve accuracy) is a huge effort, and isn't
attractive as pretty much all new CPUs have VT-x.
If Hyper-V is so great that you can't disable it you might try another
option: run VirtualBox in a Hyper-V VM which has VT-x passthrough
enabled. This isn't a config we test at all currently, but if Hyper-V
takes its job seriously it should work.
For some reason VMWare Workstation supports from 12.5 on the Anniversary
Update from Windows 10. As they won't be able to access VT-X anyway,
since HyperV uses exclusive access to it all the time I more think that
they simply removed all dependencies to the VT-x functionality.
VMware implemented SMP and 64-bit support long before VT-x was
available, so they had no choice (and a lot of time) to make it happen.
Is that an option for VirtualBox? Wouldn't the remove of VT-x feature
for VirtualBox also mean to slow down everything pretty much? Does
anyone ever tested if the performance of VMWare Workstation 12.5 is way
slower on Anniversary Update Windows 10 instead of an older Windows 10
Build?!
Not using VT-x would certainly cost a lot of performance in some
workloads (with only extremely few workloads having a tiny chance to be
a little faster than with VT-x). So it'd need a lot of work to give a
worse result. Not an attractive situation.
Benchmarking other products is something we leave to others, but I
assume that not using VT-x overall is having a performance impact.
Would be much better and simpler if Hyper-V (especially the variant
shipped in Desktop OS variants) would learn how to (optionally) share
VT-x, which is what other hypervisors can do for a long time.
Regards,
Klaus
Thanks a lot!
Regards,
Clemens
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