[PATCH v8 18/32] OvmfPkg/SecMain: validate the memory used for decompressing Fv

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

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

The VMM launch sequence should have pre-validated all the data pages used
in the Reset vector. The range does not cover the data pages used during
the SEC phase (mainly PEI and DXE firmware volume decompression memory).

When SEV-SNP is active, the memory must be pre-validated before the access.
Add support to pre-validate the memory range from SnpSecPreValidatedStart
to SnpSecPreValidatedEnd. This should be sufficent to enter into the PEI
phase.

Cc: Michael Roth <michael.roth@amd.com>
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: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkg.dec                           |  4 ++++
 .../PeiMemEncryptSevLib.inf                   |  2 ++
 OvmfPkg/Sec/SecMain.inf                       |  3 +++
 OvmfPkg/Sec/AmdSev.h                          | 23 +++++++++++++++++++
 .../X64/PeiSnpSystemRamValidate.c             |  5 ++++
 OvmfPkg/Sec/AmdSev.c                          | 22 +++++++++++++++++-
 OvmfPkg/Sec/SecMain.c                         |  5 ++++
 OvmfPkg/FvmainCompactScratchEnd.fdf.inc       |  5 ++++
 8 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index efa0de6d0600..052784c18864 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -354,6 +354,10 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|0|UINT32|0x54
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize|0|UINT32|0x55
 
+  ## The range of memory that is validated by the SEC phase.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart|0|UINT32|0x56
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd|0|UINT32|0x57
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
index 1cc9dd6691a2..291eef39ca8d 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
@@ -78,3 +78,5 @@ [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageSize
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress
   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 9523a8ea6c8f..282e60a2764f 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -51,6 +51,7 @@ [LibraryClasses]
   PeCoffExtraActionLib
   ExtractGuidedSectionLib
   LocalApicLib
+  MemEncryptSevLib
   CpuExceptionHandlerLib
 
 [Ppis]
@@ -73,6 +74,8 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
diff --git a/OvmfPkg/Sec/AmdSev.h b/OvmfPkg/Sec/AmdSev.h
index adad96d23189..411bbedae4cf 100644
--- a/OvmfPkg/Sec/AmdSev.h
+++ b/OvmfPkg/Sec/AmdSev.h
@@ -69,4 +69,27 @@ SevEsIsEnabled (
   VOID
   );
 
+/**
+ Validate System RAM used for decompressing the PEI and DXE firmware volumes
+ when SEV-SNP is active. The PCDs SecValidatedStart and SecValidatedEnd are
+ set in OvmfPkg/FvmainCompactScratchEnd.fdf.inc.
+
+**/
+VOID
+SecValidateSystemRam (
+  VOID
+  );
+
+/**
+  Determine if SEV-SNP is active.
+
+  @retval TRUE   SEV-SNP is enabled
+  @retval FALSE  SEV-SNP is not enabled
+
+**/
+BOOLEAN
+SevSnpIsEnabled (
+  VOID
+  );
+
 #endif
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
index a0803e1255dc..f8b44fe040b6 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
@@ -65,6 +65,11 @@ STATIC SNP_PRE_VALIDATED_RANGE mPreValidatedRange[] = {
     FixedPcdGet32 (PcdOvmfSecPeiTempRamBase),
     FixedPcdGet32 (PcdOvmfSecPeiTempRamBase) + FixedPcdGet32 (PcdOvmfSecPeiTempRamSize),
   },
+  // The below range is pre-validated by the Sec/SecMain.c
+  {
+    FixedPcdGet32 (PcdOvmfSecValidatedStart),
+    FixedPcdGet32 (PcdOvmfSecValidatedEnd)
+  },
 };
 
 STATIC
diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c
index 9dd42b195785..aef27d9727b2 100644
--- a/OvmfPkg/Sec/AmdSev.c
+++ b/OvmfPkg/Sec/AmdSev.c
@@ -55,7 +55,6 @@ SevEsProtocolFailure (
   @retval FALSE  SEV-SNP is not enabled
 
 **/
-STATIC
 BOOLEAN
 SevSnpIsEnabled (
   VOID
@@ -277,3 +276,24 @@ SevEsIsEnabled (
 
   return (SevEsWorkArea->SevEsEnabled != 0);
 }
+
+/**
+ Validate System RAM used for decompressing the PEI and DXE firmware volumes
+ when SEV-SNP is active. The PCDs SecValidatedStart and SecValidatedEnd are
+ set in OvmfPkg/FvmainCompactScratchEnd.fdf.inc.
+
+**/
+VOID
+SecValidateSystemRam (
+  VOID
+  )
+{
+  PHYSICAL_ADDRESS        Start, End;
+
+  if (IsSevGuest () && SevSnpIsEnabled ()) {
+    Start = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdOvmfSecValidatedStart);
+    End = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdOvmfSecValidatedEnd);
+
+    MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES (End - Start));
+  }
+}
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 406e3a25d0cd..b173ff976073 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -847,6 +847,11 @@ SecCoreStartupWithStack (
   SecCoreData.BootFirmwareVolumeBase = BootFv;
   SecCoreData.BootFirmwareVolumeSize = (UINTN) BootFv->FvLength;
 
+  //
+  // Validate the System RAM used in the SEC Phase
+  //
+  SecValidateSystemRam ();
+
   //
   // Make sure the 8259 is masked before initializing the Debug Agent and the debug timer is enabled
   //
diff --git a/OvmfPkg/FvmainCompactScratchEnd.fdf.inc b/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
index 46f52583297c..d8d45fc9aa6d 100644
--- a/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
+++ b/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
@@ -63,3 +63,8 @@
 DEFINE DECOMP_SCRATCH_BASE           = (($(DECOMP_SCRATCH_BASE_UNALIGNED) + $(DECOMP_SCRATCH_BASE_ALIGNMENT)) & $(DECOMP_SCRATCH_BASE_MASK))
 
 SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd = $(DECOMP_SCRATCH_BASE) + $(DECOMP_SCRATCH_SIZE)
+
+#
+# The range of pages that should be pre-validated during the SEC phase when SEV-SNP is active in the guest VM.
+SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart = $(MEMFD_BASE_ADDRESS) + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
+SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd = $(DECOMP_SCRATCH_BASE) + $(DECOMP_SCRATCH_SIZE)
-- 
2.25.1