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>
Signed-off-by: Min Xu <min.m.xu@intel.com>
---
 OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c       | 12 +++++++-
 .../QemuFwCfgAcpiPlatformDxe.inf              |  1 +
 .../Include/Protocol/QemuAcpiTableNotify.h    | 29 +++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h

diff --git a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c
index df800b149275..e8a9aff089e8 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
@@ -1129,7 +1132,14 @@ 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/AcpiPlatformDxe/QemuFwCfgAcpiPlatformDxe.inf b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpiPlatformDxe.inf
index dac25d1505be..6ffce2db5f99 100644
--- a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpiPlatformDxe.inf
+++ b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpiPlatformDxe.inf
@@ -48,6 +48,7 @@
 [Protocols]
   gEfiAcpiTableProtocolGuid                     # PROTOCOL ALWAYS_CONSUMED
   gEfiPciIoProtocolGuid                         # PROTOCOL SOMETIMES_CONSUMED
+  gQemuAcpiTableNotifyProtocolGuid              # PROTOCOL PRODUCES
 
 [Guids]
   gRootBridgesConnectedEventGroupGuid
diff --git a/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h b/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h
new file mode 100644
index 000000000000..8549ea9ec374
--- /dev/null
+++ b/OvmfPkg/Include/Protocol/QemuAcpiTableNotify.h
@@ -0,0 +1,29 @@
+/** @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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