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SubjectRE: [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V
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> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Thursday, January 31, 2013 2:38 AM
> To: KY Srinivasan
> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; x86@kernel.org;
> tglx@linutronix.de; devel@linuxdriverproject.org; gregkh@linuxfoundation.org;
> jasowang@redhat.com; linux-kernel@vger.kernel.org; hpa@zytor.com
> 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@microsoft.com> 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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