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

[KY Srinivasan]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, January 31, 2013 2:38 AM
> To: KY Srinivasan
> Cc: olaf@xxxxxxxxx; bp@xxxxxxxxx; apw@xxxxxxxxxxxxx; x86@xxxxxxxxxx;
> tglx@xxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
> jasowang@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; hpa@xxxxxxxxx
> Subject: RE: [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V
> 
> >>> 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.

Agreed; I will make the appropriate changes as you have recommended.

Regards,

K. Y


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