[PATCH] db: add Hyper-V leaf 0x40000001

This patch adds CPUID.40000001:EAX, the vendor-neutral Hyper-V
interface signature ("Hv#1"). It is used by COCONUT SVSM for
Hyper-V host detection before enabling Hyper-V specific paths.

Signed-off-by: Tanish Desai <[email protected]>
Link: https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/feature-discovery
---
 db/xml/leaf_40000001.xml | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 db/xml/leaf_40000001.xml

diff --git a/db/xml/leaf_40000001.xml b/db/xml/leaf_40000001.xml
new file mode 100644
index 0000000..c37bb90
--- /dev/null
+++ b/db/xml/leaf_40000001.xml
@@ -0,0 +1,29 @@
+<!--
+*** SPDX-FileCopyrightText: 2026 Linutronix GmbH
+*** SPDX-License-Identifier: GPL-2.0-only
+-->
+<leaf id="0x40000001">
+  <desc>Hypervisor interface signature</desc>
+  <text>
+    Vendor-neutral hypervisor interface identification.  This determines the
+    semantics of leaves 0x40000002 through 0x400000ff.  Software should base
+    compatibility decisions on this signature rather than the vendor ID from
+    leaf 0x40000000.
+  </text>
+  <hypervisors>
+    <hypervisor>Hyperv</hypervisor>
+  </hypervisors>
+  <subleaf id="0">
+    <eax>
+      <bit0  len="32" id="hyp_interface"           desc="Hypervisor interface signature">
+        <text>
+          Hypervisors conforming to the Microsoft hypervisor interface return
+          the ASCII signature "Hv#1" (0x31237648) in this field.
+        </text>
+        <values>
+          <value      id="0x31237648"              desc="Hv#1" />
+        </values>
+      </bit0>
+    </eax>
+  </subleaf>
+</leaf>
-- 
2.15.0