Re: [PATCH v6 6/6] OvmfPkg/AmdSevDxe: Add support for SEV live migration.


Lendacky, Thomas
 

On 8/2/21 7:33 AM, Ashish Kalra wrote:
From: Ashish Kalra <ashish.kalra@...>

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

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@...>
---
OvmfPkg/AmdSevDxe/AmdSevDxe.c | 64 ++++++++++++++++++++
OvmfPkg/AmdSevDxe/AmdSevDxe.inf | 4 ++
OvmfPkg/Include/Guid/AmdSevMemEncryptLib.h | 20 ++++++
OvmfPkg/OvmfPkg.dec | 1 +
4 files changed, 89 insertions(+)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index c66c4e9b92..bfad71b9c6 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -15,10 +15,47 @@
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/DxeServicesTableLib.h>
+#include <Library/UefiRuntimeServicesTableLib.h>
+#include <Library/UefiBootServicesTableLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/MemoryAllocationLib.h>
+#include <Guid/AmdSevMemEncryptLib.h>
+#include <Guid/EventGroup.h>
#include <Library/PcdLib.h>

+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 (
@@ -30,6 +67,7 @@ AmdSevDxeEntryPoint (
EFI_GCD_MEMORY_SPACE_DESCRIPTOR *AllDescMap;
UINTN NumEntries;
UINTN Index;
+ EFI_EVENT Event;

//
// Do nothing when SEV is not enabled
@@ -130,5 +168,31 @@ 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_INFO, "%a: CreateEventEx(): %r\n",
DEBUG_ERROR?

+ __FUNCTION__, Status));
Should there be an "ASSERT_EFI_ERROR (Status)" after the DEBUG call?

Thanks,
Tom

+ }
+
return EFI_SUCCESS;
}
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
index 0676fcc5b6..2ad1fb8632 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
@@ -45,3 +45,7 @@

[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 0000000000..8ab283860b
--- /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 2ab27f0c73..3978852557 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -125,6 +125,7 @@
gQemuKernelLoaderFsMediaGuid = {0x1428f772, 0xb64a, 0x441e, {0xb8, 0xc3, 0x9e, 0xbd, 0xd7, 0xf8, 0x93, 0xc7}}
gGrubFileGuid = {0xb5ae312c, 0xbc8a, 0x43b1, {0x9c, 0x62, 0xeb, 0xb8, 0x26, 0xdd, 0x5d, 0x07}}
gConfidentialComputingSecretGuid = {0xadf956ad, 0xe98c, 0x484c, {0xae, 0x11, 0xb5, 0x1c, 0x7d, 0x33, 0x64, 0x47}}
+ 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

Join devel@edk2.groups.io to automatically receive all group messages.