[PATCH v1 3/8] OvmfPkg/AmdSev: add a page to the MEMFD for firmware config hashes

[Dov Murik <dovmurik@linux.ibm.com>]

From: James Bottomley <jejb@linux.ibm.com>

Reserve a page inside the MEMFD for the VMM to place an encrypted page
containing GUID described hashes of firmware configurations.  We do
this so the page gets attested by the PSP and thus the untrusted VMM
can't pass in different files from what the guest owner thinks.

Declare this in the Reset Vector table using GUID
7255371f-3a3b-4b04-927b-1da6efa8d454 and a uint32_t table of a base
and size value, identically to the secret block.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.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: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
---
 OvmfPkg/OvmfPkg.dec                          |  6 ++++++
 OvmfPkg/AmdSev/AmdSevX64.fdf                 |  3 +++
 OvmfPkg/ResetVector/ResetVector.inf          |  2 ++
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 20 ++++++++++++++++++++
 OvmfPkg/ResetVector/ResetVector.nasmb        |  2 ++
 5 files changed, 33 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 6ae733f6e39f..7cd29a60a436 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 a hash table confirming allowed
+  #  parameters to be passed in via the Qemu firmware configuration
+  #  device
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|0x0|UINT32|0x47
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize|0x0|UINT32|0x48
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/AmdSev/AmdSevX64.fdf b/OvmfPkg/AmdSev/AmdSevX64.fdf
index dd0030dbf189..6e1bb7723bd1 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.fdf
+++ b/OvmfPkg/AmdSev/AmdSevX64.fdf
@@ -65,6 +65,9 @@ [FD.MEMFD]
 0x00D000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
 
+0x00E000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
+
 0x010000|0x010000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index dc38f68919cd..d028c92d8cfa 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -47,3 +47,5 @@ [Pcd]
 [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
index 9c0b5853a46f..7ec3c6e980c3 100644
--- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
@@ -47,7 +47,27 @@ TIMES (15 - ((guidedStructureEnd - guidedStructureStart + 15) % 16)) DB 0
 ;
 guidedStructureStart:
 
+; SEV Hash Table Block
 ;
+; This describes the guest ram area where the hypervisor should
+; install a table describing the hashes of certain firmware configuration
+; device files that would otherwise be passed in unchecked.  The current
+; use is for the kernel, initrd and command line values, but others may be
+; added.  The data format is:
+;
+; base physical address (32 bit word)
+; table length (32 bit word)
+;
+; GUID (SEV FW config hash block): 7255371f-3a3b-4b04-927b-1da6efa8d454
+;
+sevFwHashBlockStart:
+    DD      SEV_FW_HASH_BLOCK_BASE
+    DD      SEV_FW_HASH_BLOCK_SIZE
+    DW      sevFwHashBlockEnd - sevFwHashBlockStart
+    DB      0x1f, 0x37, 0x55, 0x72, 0x3b, 0x3a, 0x04, 0x4b
+    DB      0x92, 0x7b, 0x1d, 0xa6, 0xef, 0xa8, 0xd4, 0x54
+sevFwHashBlockEnd:
+
 ; SEV Secret block
 ;
 ; This describes the guest ram area where the hypervisor should
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 5fbacaed5f9d..8d0bab02f8cb 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -88,5 +88,7 @@
   %define SEV_ES_AP_RESET_IP  FixedPcdGet32 (PcdSevEsWorkAreaBase)
   %define SEV_LAUNCH_SECRET_BASE  FixedPcdGet32 (PcdSevLaunchSecretBase)
   %define SEV_LAUNCH_SECRET_SIZE  FixedPcdGet32 (PcdSevLaunchSecretSize)
+  %define SEV_FW_HASH_BLOCK_BASE  FixedPcdGet32 (PcdQemuHashTableBase)
+  %define SEV_FW_HASH_BLOCK_SIZE  FixedPcdGet32 (PcdQemuHashTableSize)
 %include "Ia16/ResetVectorVtf0.asm"
 
-- 
2.25.1