RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

In TDX the guest firmware is designed to publish a multiprocessor-wakeup
structure to let the guest-bootstrap processor wake up guest-application
processors with a mailbox. The mailbox is memory that the guest firmware
can reserve so each guest virtual processor can have the guest OS send
a message to them. The address of the mailbox is recorded in the MADT
table. See [ACPI].

To maintain the simplicity of the AcpiPlatformDxe, the MADT ACPI table
will be altered in another driver (TdxDxe) by installing a protocol
to notify that the ACPI table provided by Qemu is ready. Then in TdxDxe
a notification functioin will be called to alter the MADT table to recorded
the mailbox address.

The protocol is gQemuAcpiTableNotifyProtocolGuid.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
---
 OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf   |  1 +
 OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c       | 14 +++++++++-
 .../Include/Protocol/QemuAcpiTableNotify.h    | 27 +++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h

diff --git a/OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf b/OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf
index f22bd7cb6da1..09daf30bcd3d 100644
--- a/OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf
+++ b/OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf
@@ -49,6 +49,7 @@
 [Protocols]
   gEfiAcpiTableProtocolGuid                     # PROTOCOL ALWAYS_CONSUMED
   gEfiPciIoProtocolGuid                         # PROTOCOL SOMETIMES_CONSUMED
+  gQemuAcpiTableNotifyProtocolGuid              # PROTOCOL PRODUCES
 
 [Guids]
   gRootBridgesConnectedEventGroupGuid
diff --git a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c
index b885965a601e..c8dee17c13e6 100644
--- a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c
+++ b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c
@@ -19,7 +19,10 @@
 #include <Library/QemuFwCfgS3Lib.h>           // QemuFwCfgS3Enabled()
 #include <Library/UefiBootServicesTableLib.h> // gBS
 
+#include <Protocol/QemuAcpiTableNotify.h>
 #include "AcpiPlatform.h"
+EFI_HANDLE                       mQemuAcpiHandle = NULL;
+QEMU_ACPI_TABLE_NOTIFY_PROTOCOL  mAcpiNotifyProtocol;
 
 //
 // The user structure for the ordered collection that will track the fw_cfg
@@ -1273,7 +1276,16 @@ UninstallAcpiTables:
       AcpiProtocol->UninstallAcpiTable (AcpiProtocol, InstalledKey[Installed]);
     }
   } else {
-    DEBUG ((DEBUG_INFO, "%a: installed %d tables\n", __FUNCTION__, Installed));
+    //
+    // Install a protocol to notify that the ACPI table provided by Qemu is
+    // ready.
+    //
+    gBS->InstallProtocolInterface (
+           &mQemuAcpiHandle,
+           &gQemuAcpiTableNotifyProtocolGuid,
+           EFI_NATIVE_INTERFACE,
+           &mAcpiNotifyProtocol
+           );
   }
 
   for (SeenPointerEntry = OrderedCollectionMin (SeenPointers);
diff --git a/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h b/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h
new file mode 100644
index 000000000000..a3dd2fc1dc91
--- /dev/null
+++ b/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h
@@ -0,0 +1,27 @@
+/** @file
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef QEMU_ACPI_TABLE_NOTIFY_H_
+#define QEMU_ACPI_TABLE_NOTIFY_H_
+
+#define QEMU_ACPI_TABLE_NOTIFY_GUID \
+  { 0x928939b2, 0x4235, 0x462f, { 0x95, 0x80, 0xf6, 0xa2, 0xb2, 0xc2, 0x1a, 0x4f } };
+
+///
+/// Forward declaration
+///
+typedef struct _QEMU_ACPI_TABLE_NOTIFY_PROTOCOL QEMU_ACPI_TABLE_NOTIFY_PROTOCOL;
+
+///
+/// Protocol structure
+///
+struct _QEMU_ACPI_TABLE_NOTIFY_PROTOCOL {
+  UINT8    Notify;
+};
+
+extern EFI_GUID  gQemuAcpiTableNotifyProtocolGuid;
+
+#endif
-- 
2.29.2.windows.2



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