[PATCH RFC v3 06/22] OvmfPkg: reserve CPUID page for the SEV-SNP guest

["Brijesh Singh" <brijesh.singh@amd.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

During the SEV-SNP guest launch sequence, two special pages need to be
inserted, the secrets and CPUID. The secrets page, contain the VM
platform communication keys. The guest BIOS and/or OS can use this key
to communicate with the SEV firmware to get the attestation report.
The CPUID page, contain the CPUIDs entries filtered through the AMD-SEV
firmware.

OvmfPkg already reserves the memory for the Secrets Page in the MEMFD.
Extend the MEMFD to reserve the memory for the CPUID page.

See SEV-SNP spec for more information on the content layout of the secrets
and CPUID page, and how it can be used by the SEV-SNP guest VM.

Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkg.dec                          |  6 ++++++
 OvmfPkg/OvmfPkgX64.fdf                       |  3 +++
 OvmfPkg/PlatformPei/PlatformPei.inf          |  2 ++
 OvmfPkg/ResetVector/ResetVector.inf          |  2 ++
 OvmfPkg/PlatformPei/MemDetect.c              | 12 ++++++++++++
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 18 ++++++++++++++++++
 OvmfPkg/ResetVector/ResetVector.nasmb        |  2 ++
 7 files changed, 45 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 6ae733f6e39f..fdb5dacdc7fa 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -321,6 +321,12 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|0x0|UINT32|0x42
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize|0x0|UINT32|0x43
 
+  ## The base address and size of the SEV-SNP CPUID Area provisioned by the
+  #  SEV-SNP firmware. If this is set in the .fdf, the platform
+  #  is responsible for protecting the area from DXE phase overwrites.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidBase|0x0|UINT32|0x47
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidSize|0x0|UINT32|0x48
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 9126b8eb5014..1300af666c49 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -91,6 +91,9 @@ [FD.MEMFD]
 0x00D000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
 
+0x00E000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidSize
+
 0x010000|0x010000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 3256ccfe88d8..89c8e9627c86 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -120,6 +120,8 @@ [FixedPcd]
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiReservedMemoryType
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiRuntimeServicesCode
   gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiRuntimeServicesData
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index dc38f68919cd..8e52265602c3 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -45,5 +45,7 @@ [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
 [FixedPcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpCpuidSize
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index c08aa2e45a53..483e92af8219 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -894,6 +894,18 @@ InitializeRamRegions (
         EfiACPIMemoryNVS
         );
     }
+
+    if (MemEncryptSevSnpIsEnabled ()) {
+      //
+      // If SEV-SNP is enabled, reserve the CPUID page. The memory range should
+      // not be treated as a RAM by the guest OS, so, mark it as reserved.
+      //
+      BuildMemoryAllocationHob (
+        (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSnpCpuidBase),
+        (UINT64)(UINTN) PcdGet32 (PcdOvmfSnpCpuidSize),
+        EfiReservedMemoryType
+      );
+    }
 #endif
   }
 
diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
index 9c0b5853a46f..05c7e32f46a0 100644
--- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
@@ -47,6 +47,24 @@ TIMES (15 - ((guidedStructureEnd - guidedStructureStart + 15) % 16)) DB 0
 ;
 guidedStructureStart:
 
+;
+; SEV-SNP boot support
+;
+; sevSnpBlock:
+;   For the initial boot of SEV-SNP guest, a CPUID page must be reserved by
+;   the BIOS at a RAM area defined by SEV_SNP_CPUID_BASE. A hypervisor will
+;   locate this information using the SEV-SNP boot block GUID.
+;
+; GUID (SEV-SNP boot block): bd39c0c2-2f8e-4243-83e8-1b74cebcb7d9
+;
+sevSnpBootBlockStart:
+    DD      SNP_CPUID_BASE
+    DD      SNP_CPUID_SIZE
+    DW      sevSnpBootBlockEnd - sevSnpBootBlockStart
+    DB      0xC2, 0xC0, 0x39, 0xBD, 0x8e, 0x2F, 0x43, 0x42
+    DB      0x83, 0xE8, 0x1B, 0x74, 0xCE, 0xBC, 0xB7, 0xD9
+sevSnpBootBlockEnd:
+
 ;
 ; SEV Secret block
 ;
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 5beba3ecb290..36739096e7e1 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -90,5 +90,7 @@
   %define SEV_ES_AP_RESET_IP  FixedPcdGet32 (PcdSevEsWorkAreaBase)
   %define SEV_LAUNCH_SECRET_BASE  FixedPcdGet32 (PcdSevLaunchSecretBase)
   %define SEV_LAUNCH_SECRET_SIZE  FixedPcdGet32 (PcdSevLaunchSecretSize)
+  %define SNP_CPUID_BASE  FixedPcdGet32 (PcdOvmfSnpCpuidBase)
+  %define SNP_CPUID_SIZE  FixedPcdGet32 (PcdOvmfSnpCpuidSize)
 %include "Ia16/ResetVectorVtf0.asm"
 
-- 
2.17.1