From 8d82fca148d9564b666b5f4185a0e78e1f77e230 Mon Sep 17 00:00:00 2001
From: Ashish Kalra <ashish.kalra@amd.com>
Date: Tue, 5 Apr 2022 16:40:03 +0000
Subject: [PATCH 6/9] OvmfPkg/AmdSevDxe: Add support for SEV live migration.

cherry-picked from https://patchew.org/EDK2/cover.1629380011.git.ashish.kalra@amd.com .

Check for SEV live migration feature support, if detected
setup a new UEFI enviroment variable to indicate OVMF
support for SEV live migration.

This environment variable is created by UEFI but consumed
by the (guest) linux kernel. This is actually part of a
3-way negotiation of the live migration feature between
hypervisor, guest OVMF and guest kernel. Host indicates
support for live migration, which is detected by OVMF
and correspondingly OVMF sets this SetLiveMigrationEnabled
UEFI variable, which is read by the guest kernel and it
indicates to the guest kernel that both host and OVMF
support and have enabled the live migration feature.

The new runtime UEFI environment variable is set via the
notification function registered for the
EFI_END_OF_DXE_EVENT_GROUP_GUID event in AmdSevDxe driver.

AmdSevDxe module is an apriori driver so it gets loaded between PEI
and DXE phases and the SetVariable call will fail at the driver's
entry point as the Variable DXE module is still not loaded yet.
So we need to wait for an event notification which is signaled
after the Variable DXE module is loaded, hence, using the
EndOfDxe event notification to make this call.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 OvmfPkg/AmdSevDxe/AmdSevDxe.c              | 67 ++++++++++++++++++++++
 OvmfPkg/AmdSevDxe/AmdSevDxe.inf            |  4 ++
 OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h | 20 +++++++
 OvmfPkg/OvmfPkg.dec                        |  1 +
 4 files changed, 92 insertions(+)
 create mode 100644 OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index db3675ae..e3a8049d 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -15,10 +15,13 @@
 #include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
 #include <Library/DxeServicesTableLib.h>
+#include <Library/UefiRuntimeServicesTableLib.h>
 #include <Library/MemEncryptSevLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Guid/ConfidentialComputingSevSnpBlob.h>
+#include <Guid/AmdSevMemEncryptLib.h>
+#include <Guid/EventGroup.h>
 #include <Library/PcdLib.h>
 #include <Pi/PrePiDxeCis.h>
 #include <Protocol/SevMemoryAcceptance.h>
@@ -191,6 +194,39 @@ STATIC EDKII_MEMORY_ACCEPT_PROTOCOL  mMemoryAcceptProtocol = {
   AmdSevMemoryAccept
 };
 
+STATIC
+VOID
+EFIAPI
+AmdSevDxeOnEndOfDxe (
+  IN EFI_EVENT  Event,
+  IN VOID       *EventToSignal
+  )
+{
+  EFI_STATUS  Status;
+  BOOLEAN     SevLiveMigrationEnabled;
+
+  SevLiveMigrationEnabled = MemEncryptSevLiveMigrationIsEnabled ();
+
+  if (SevLiveMigrationEnabled) {
+    Status = gRT->SetVariable (
+                    L"SevLiveMigrationEnabled",
+                    &gAmdSevMemEncryptGuid,
+                    EFI_VARIABLE_NON_VOLATILE |
+                    EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                    EFI_VARIABLE_RUNTIME_ACCESS,
+                    sizeof SevLiveMigrationEnabled,
+                    &SevLiveMigrationEnabled
+                    );
+
+    DEBUG ((
+      DEBUG_INFO,
+      "%a: Setting SevLiveMigrationEnabled variable, status = %lx\n",
+      __FUNCTION__,
+      Status
+      ));
+  }
+}
+
 EFI_STATUS
 EFIAPI
 AmdSevDxeEntryPoint (
@@ -203,6 +239,7 @@ AmdSevDxeEntryPoint (
   UINTN                                     NumEntries;
   UINTN                                     Index;
   CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
+  EFI_EVENT                                 Event;
 
   //
   // Do nothing when SEV is not enabled
@@ -361,5 +398,35 @@ AmdSevDxeEntryPoint (
                   );
   }
 
+  //
+  // AmdSevDxe module is an apriori driver so it gets loaded between PEI
+  // and DXE phases and the SetVariable call will fail at the driver's
+  // entry point as the Variable DXE module is still not loaded yet.
+  // So we need to wait for an event notification which is signaled
+  // after the Variable DXE module is loaded, hence, using the
+  // EndOfDxe event notification to make this call.
+  //
+  // Register EFI_END_OF_DXE_EVENT_GROUP_GUID event.
+  // The notification function sets the runtime variable indicating OVMF
+  // support for SEV live migration.
+  //
+  Status = gBS->CreateEventEx (
+                  EVT_NOTIFY_SIGNAL,
+                  TPL_CALLBACK,
+                  AmdSevDxeOnEndOfDxe,
+                  NULL,
+                  &gEfiEndOfDxeEventGroupGuid,
+                  &Event
+                  );
+
+  if (EFI_ERROR (Status)) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a: CreateEventEx(): %r\n",
+      __FUNCTION__,
+      Status
+      ));
+  }
+
   return EFI_SUCCESS;
 }
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
index e7c7d526..dd1da527 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
@@ -57,3 +57,7 @@
 
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId
+
+[Guids]
+  gAmdSevMemEncryptGuid
+  gEfiEndOfDxeEventGroupGuid         ## CONSUMES   ## Event
diff --git a/OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h b/OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h
new file mode 100644
index 00000000..62d22e79
--- /dev/null
+++ b/OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h
@@ -0,0 +1,20 @@
+/** @file
+
+  AMD Memory Encryption GUID, define a new GUID for defining
+  new UEFI environment variables assocaiated with SEV Memory Encryption.
+
+  Copyright (c) 2021, AMD Inc. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef __AMD_SEV_MEMENCRYPT_LIB_H__
+#define __AMD_SEV_MEMENCRYPT_LIB_H__
+
+#define AMD_SEV_MEMENCRYPT_GUID \
+{0x0cf29b71, 0x9e51, 0x433a, {0xa3, 0xb7, 0x81, 0xf3, 0xab, 0x16, 0xb8, 0x75}}
+
+extern EFI_GUID  gAmdSevMemEncryptGuid;
+
+#endif
diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 34bca309..d50b1ae3 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -170,6 +170,7 @@
   gUefiOvmfPkgTdxAcpiHobGuid            = {0x6a0c5870, 0xd4ed, 0x44f4, {0xa1, 0x35, 0xdd, 0x23, 0x8b, 0x6f, 0x0c, 0x8d}}
   gEfiNonCcFvGuid                       = {0xae047c6d, 0xbce9, 0x426c, {0xae, 0x03, 0xa6, 0x8e, 0x3b, 0x8a, 0x04, 0x88}}
   gOvmfVariableGuid                     = {0x50bea1e5, 0xa2c5, 0x46e9, {0x9b, 0x3a, 0x59, 0x59, 0x65, 0x16, 0xb0, 0x0a}}
+  gAmdSevMemEncryptGuid                 = {0x0cf29b71, 0x9e51, 0x433a, {0xa3, 0xb7, 0x81, 0xf3, 0xab, 0x16, 0xb8, 0x75}}
 
 [Ppis]
   # PPI whose presence in the PPI database signals that the TPM base address
-- 
2.25.1