OvmfPkg: Create a calling area used to communicate with the SVSM

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

An SVSM requires a calling area page whose address (CAA) is used by the
SVSM to communicate and process the SVSM request.

Add a pre-defined page area to the OvmfPkg and AmdSev packages and define
corresponding PCDs used to communicate the location and size of the area.
Keep the AmdSev package in sync with the OvmfPkg and adjust the AmdSev
launch and hash area memory locations.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Min Xu <min.m.xu@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

OvmfPkg/AmdSev/AmdSevX64.fdf

@@ -68,13 +68,16 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase|gUefiOvmfPkgTokenSpaceGuid.PcdO
 0x00E000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize
 
-0x00F000|0x000C00
+0x00F000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize
+
+0x010000|0x000C00
 gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
 
-0x00FC00|0x000400
+0x010C00|0x000400
 gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
 
-0x010000|0x010000
+0x011000|0x00F000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
 0x020000|0x0E0000

OvmfPkg/OvmfPkg.dec

@@ -338,6 +338,10 @@
   ## Restrict boot to EFI applications in firmware volumes.
   gUefiOvmfPkgTokenSpaceGuid.PcdBootRestrictToFirmware|FALSE|BOOLEAN|0x6c
 
+  ## The base address and size of the initial SVSM Calling Area.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase|0|UINT32|0x70
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize|0|UINT32|0x71
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10

OvmfPkg/OvmfPkgX64.fdf

@@ -94,6 +94,9 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase|gUefiOvmfPkgTokenSpaceGuid.PcdO
 0x00E000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize
 
+0x00F000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize
+
 0x010000|0x010000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 

OvmfPkg/PlatformPei/AmdSev.c

@@ -555,5 +555,16 @@ SevInitializeRam (
       (UINT64)(UINTN)PcdGet32 (PcdOvmfCpuidSize),
       EfiReservedMemoryType
       );
+
+    //
+    // The calling area memory needs to be protected until the OS can create
+    // its own calling area. Mark it as EfiReservedMemoryType so that the
+    // guest firmware and OS do not use it as a system memory.
+    //
+    BuildMemoryAllocationHob (
+      (EFI_PHYSICAL_ADDRESS)(UINTN)PcdGet32 (PcdOvmfSecSvsmCaaBase),
+      (UINT64)(UINTN)PcdGet32 (PcdOvmfSecSvsmCaaSize),
+      EfiReservedMemoryType
+      );
   }
 }

OvmfPkg/PlatformPei/PlatformPei.inf

@@ -128,6 +128,8 @@
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiRuntimeServicesData
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase

OvmfPkg/ResetVector/ResetVector.inf

@@ -62,6 +62,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdUse5LevelPageTable

OvmfPkg/ResetVector/ResetVector.nasmb

@@ -3,7 +3,7 @@
 ; This file includes all other code files to assemble the reset vector code
 ;
 ; Copyright (c) 2008 - 2013, Intel Corporation. All rights reserved.<BR>
-; Copyright (c) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; Copyright (c) 2020 - 2024, Advanced Micro Devices, Inc. All rights reserved.<BR>
 ; SPDX-License-Identifier: BSD-2-Clause-Patent
 ;
 ;------------------------------------------------------------------------------
@@ -69,6 +69,8 @@
 %define SEV_SNP_SECRETS_SIZE          (FixedPcdGet32 (PcdOvmfSnpSecretsSize))
 %define CPUID_BASE                    (FixedPcdGet32 (PcdOvmfCpuidBase))
 %define CPUID_SIZE                    (FixedPcdGet32 (PcdOvmfCpuidSize))
+%define SVSM_CAA_BASE                 (FixedPcdGet32 (PcdOvmfSecSvsmCaaBase))
+%define SVSM_CAA_SIZE                 (FixedPcdGet32 (PcdOvmfSecSvsmCaaSize))
 %if (FixedPcdGet32 (PcdSevLaunchSecretBase) > 0)
   ; There's a reserved page for SEV secrets and hashes; the VMM will fill and
   ; validate the page, or mark it as a zero page.
@@ -89,7 +91,7 @@
 ;
 %define SNP_SEC_MEM_BASE_DESC_2       (GHCB_BASE + 0x1000)
 %define SNP_SEC_MEM_SIZE_DESC_2       (SEV_SNP_SECRETS_BASE - SNP_SEC_MEM_BASE_DESC_2)
-%define SNP_SEC_MEM_BASE_DESC_3       (CPUID_BASE + CPUID_SIZE + SEV_SNP_KERNEL_HASHES_SIZE)
+%define SNP_SEC_MEM_BASE_DESC_3       (SVSM_CAA_BASE + SVSM_CAA_SIZE + SEV_SNP_KERNEL_HASHES_SIZE)
 %define SNP_SEC_MEM_SIZE_DESC_3       (FixedPcdGet32 (PcdOvmfPeiMemFvBase) - SNP_SEC_MEM_BASE_DESC_3)
 
 %ifdef ARCH_X64

OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm

@@ -2,7 +2,7 @@
 ; @file
 ; OVMF metadata for the AMD SEV confidential computing guests
 ;
-; Copyright (c) 2021, AMD Inc. All rights reserved.<BR>
+; Copyright (c) 2021 - 2024, AMD Inc. All rights reserved.<BR>
 ;
 ; SPDX-License-Identifier: BSD-2-Clause-Patent
 ;-----------------------------------------------------------------------------
@@ -26,6 +26,9 @@ BITS  64
 ;
 %define OVMF_SECTION_TYPE_CPUID           0x3
 
+; The SVSM Calling Area Address (CAA)
+%define OVMF_SECTION_TYPE_SVSM_CAA        0x4
+
 ; Kernel hashes section for measured direct boot
 %define OVMF_SECTION_TYPE_KERNEL_HASHES   0x10
 
@@ -67,6 +70,12 @@ CpuidSec:
   DD  CPUID_SIZE
   DD  OVMF_SECTION_TYPE_CPUID
 
+; SVSM CAA page
+SvsmCaa:
+  DD  SVSM_CAA_BASE
+  DD  SVSM_CAA_SIZE
+  DD  OVMF_SECTION_TYPE_SVSM_CAA
+
 %if (SEV_SNP_KERNEL_HASHES_BASE > 0)
 ; Kernel hashes for measured direct boot, or zero page if
 ; there are no kernel hashes / SEV secrets