Document HV_X64_REGISTER_SEV_GPA_PAGE, HvX64RegisterSevAvicGpa

Author: ericlemsft

virtualization/hyper-v-on-windows/tlfs/datatypes/TOC.yml

@@ -51,4 +51,6 @@
 - name: HV_X64_TABLE_REGISTER
   href: HV_X64_TABLE_REGISTER.md
 - name: HV_X64_XMM_CONTROL_STATUS_REGISTER
-  href: HV_X64_XMM_CONTROL_STATUS_REGISTER.md
+  href: HV_X64_XMM_CONTROL_STATUS_REGISTER.md
+- name: HV_X64_REGISTER_SEV_GPA_PAGE
+  href: HV_X64_REGISTER_SEV_GPA_PAGE.md

virtualization/hyper-v-on-windows/tlfs/datatypes/hv_register_name.md

@@ -195,6 +195,7 @@ The following table lists all register names:
 | HvRegisterVpAssistPage                 | 0x00090013      |                                      |
 | HvRegisterReferenceTsc                 | 0x00090017      |                                      |
 | HvRegisterReferenceTscSequence         | 0x0009001A      |                                      |
+| HvX64RegisterSevAvicGpa                | 0x00090043      | See  [HV_X64_REGISTER_SEV_GPA_PAGE](./hv_x64_register_sev_gpa_page.md) |
 | HvRegisterSint0                        | 0x000A0000      |                                      |
 | HvRegisterSint1                        | 0x000A0001      |                                      |
 | HvRegisterSint2                        | 0x000A0002      |                                      |

virtualization/hyper-v-on-windows/tlfs/datatypes/hv_x64_register_sev_gpa_page.md

@@ -0,0 +1,29 @@
+---
+title: HV_X64_REGISTER_SEV_GPA_PAGE
+description: HV_X64_REGISTER_SEV_GPA_PAGE
+keywords: hyper-v
+author: ericle
+ms.author: hvdev
+ms.date: 08/11/2025
+ms.topic: reference
+---
+
+# HV_X64_REGISTER_SEV_GPA_PAGE
+
+The following data structure is used to define the contents of the Secure AVIC control register (HvX64RegisterSevAvicGpa).
+
+## Syntax
+
+ ```c
+typedef union
+{
+    UINT64 AsUINT64;
+    struct
+    {
+        UINT64 Enabled      : 1;
+        UINT64 ReservedZ    : 11;
+        UINT64 PageNumber   : 52;
+    };
+
+} HV_X64_REGISTER_SEV_GPA_PAGE;
+ ```