[Xen-devel] [PATCH 3/7] x86/viridian: don't put Xen version information in CPUID leaf 2

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

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 hard-code the kernel major and minor
versions from Windows Server 2008.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/hvm/viridian.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 59d76d5..433035e 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -134,8 +134,8 @@ void cpuid_viridian_leaves(const struct vcpu *v, uint32_t 
leaf,
            own version number. */
         if ( d->arch.hvm_domain.viridian.guest_os_id.raw == 0 )
             break;
-        res->a = 1; /* Build number */
-        res->b = (xen_major_version() << 16) | xen_minor_version();
+        res->a = 0; /* Build number */
+        res->b = 0x00060000; /* Windows Server 2008 */
         res->c = 0; /* SP */
         res->d = 0; /* Service branch and number */
         break;
-- 
2.1.4


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