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

[Jan Beulich]

>>> On 30.01.13 at 19:12, KY Srinivasan <kys@xxxxxxxxxxxxx> wrote:
> Presumably, Hyper-V emulation is only to run enlightened Windows. The issue 
> with
> Xen is not that it emulates Hyper-V, but this emulation is turned on while 
> running Linux.
> That is the reason I chose to check for Xen. Would you prefer a DMI check 
> for the Hyper-V
> platform. 

I consider DMI checks to be too fragile here - in particular with
the eventual passing through of host DMI attributes to guests,
this sets you up for mistakes. Instead, I would envision you
scanning the whole CPUID range "reserved" for virtualization
(starting at 0x40000000) and see whether you get back
anything other than the Hyper-V identification (much like the
way xen_cpuid_base() scans for the Xen range). Of course
that's under the premise that you're right in assuming Hyper-V
would never emulate any other hypervisor's interface.

Jan

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