Re: [Xen-devel] [PATCH v5 1/3] x86/viridian: don't put Xen version information in CPUID leaf 2

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.03.17 at 16:28, <paul.durrant@xxxxxxxxxx> wrote:
> The Hypervisor Top Level Functional Specification v5.0a states in section
> 2.5:
> 
> "The hypervisor version information is encoded in leaf 0x40000002. Two
> version numbers are provided: the main version and the service version.
> The main version includes a major and minor version number and a build
> number. These correspond to Microsoft Windows release numbers."
> 
> It also goes on to advise clients (i.e. guest versions of Windows) to use
> the following algorithm to determine compatibility with the hypervisor
> enlightenments:
> 
> if <your-main-version> greater than <hypervisor-main-version>
> {
>       your version is compatible
> }
> else if <your-main-version> equal to <hypervisor-main-version> and
>  <your-service-version> greater than or equal to <hypervisor-service-version>
> {
>       your version is compatible
> }
> else
> {
>       your version is NOT compatible
> }
> 
> So, clearly putting Xen hypervisor version information in that leaf is
> spurious, but we probably get away with it because Xen's major version
> is lower than the major version of Windows in which Hyper-V first
> appeared (Server 2008).
> 
> This patch changes the leaf to use the kernel major and minor
> versions, and build number from Windows Server 2008 (64-bit) by default.
> These default values can be overriden from the Xen command line using new
> 'viridian-version' parameter.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>



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