[PATCH v3 4/6] OvmfPkg: create a SEV secret area in the AmdSev memfd

["James Bottomley" <jejb@linux.ibm.com>]

SEV needs an area to place an injected secret where OVMF can find it
and pass it up as a ConfigurationTable.  This patch implements the
area itself as an addition to the SEV enhanced reset vector table using
an additional guid (4c2eb361-7d9b-4cc3-8081-127c90d3d294).

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3077
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

---

v2: move guid to OVMF token space, separate patches
v3: comment rewording

SEV Secret
---
 OvmfPkg/OvmfPkg.dec                          |  6 ++++++
 OvmfPkg/ResetVector/ResetVector.inf          |  4 ++++
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 19 +++++++++++++++++++
 OvmfPkg/ResetVector/ResetVector.nasmb        |  2 ++
 4 files changed, 31 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 3fbf7a0ee1a4..7d27f8e16040 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -304,6 +304,12 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|0|UINT32|0x40
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize|0|UINT32|0x41
 
+  ## The base address and size of the SEV Launch Secret Area provisioned
+  #  after remote attestation.  If this is set in the .fdf, the platform
+  #  is responsible for protecting the area from DXE phase overwrites.
+  gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|0x0|UINT32|0x42
+  gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize|0x0|UINT32|0x43
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index a53ae6c194ae..dc38f68919cd 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -43,3 +43,7 @@ [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
+
+[FixedPcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
index 9e0a74fddfc1..5c6df5ee1a31 100644
--- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
@@ -47,6 +47,25 @@ TIMES (15 - ((guidedStructureEnd - guidedStructureStart + 15) % 16)) DB 0
 ;
 guidedStructureStart:
 
+;
+; SEV Secret block
+;
+; This describes the guest ram area where the hypervisor may should
+; inject the secret.  The data format is:
+;
+; base physical address (32 bit word)
+; table length (32 bit word)
+;
+; GUID (SEV secret block): 4c2eb361-7d9b-4cc3-8081-127c90d3d294
+;
+sevSecretBlockStart:
+    DD      SEV_LAUNCH_SECRET_BASE
+    DD      SEV_LAUNCH_SECRET_SIZE
+    DW      sevSecretBlockEnd - sevSecretBlockStart
+    DB      0x61, 0xB3, 0x2E, 0x4C, 0x9B, 0x7D, 0xC3, 0x4C
+    DB      0x80, 0x81, 0x12, 0x7C, 0x90, 0xD3, 0xD2, 0x94
+sevSecretBlockEnd:
+
 ;
 ; SEV-ES Processor Reset support
 ;
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 4913b379a993..c5e0fe93abf4 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -83,5 +83,7 @@
 %include "Main.asm"
 
   %define SEV_ES_AP_RESET_IP  FixedPcdGet32 (PcdSevEsWorkAreaBase)
+  %define SEV_LAUNCH_SECRET_BASE  FixedPcdGet32 (PcdSevLaunchSecretBase)
+  %define SEV_LAUNCH_SECRET_SIZE  FixedPcdGet32 (PcdSevLaunchSecretSize)
 %include "Ia16/ResetVectorVtf0.asm"
 
-- 
2.26.2