[PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V

[H. Peter Anvin]

On 01/30/2013 12:53 AM, Jan Beulich wrote:
> 
> I'm not convinced that's the right approach - any hypervisor
> could do similar emulation, and hence you either want to make
> sure you run on Hyper-V (by excluding all others), or you
> tolerate using the emulation (which may require syncing up with
> the other guest implementations so that shared resources don't
> get used by two parties).
> 
> I also wonder whether using the Hyper-V emulation (where
> useful, there might not be anything right now, but this may
> change going forward) when no Xen support is configured
> wouldn't be better than not using anything...
> 

I'm confused about "the right approach" here is.  As far as I
understand, this only can affect a Xen guest where HyperV guest support
is enabled but not Xen support, and only because Xen emulates HyperV but
does so incorrectly.

This is a Xen bug, and as such it makes sense to reject Xen
specifically.  If another hypervisor emulates HyperV and does so
correctly there seems to be no reason to reject it.

	-hpa