[PATCH v6 18/29] OvmfPkg/SecMain: pre-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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkg.dec                           |  5 ++++
 .../PeiMemEncryptSevLib.inf                   |  2 ++
 OvmfPkg/Sec/SecMain.inf                       |  3 +++
 OvmfPkg/Sec/AmdSev.h                          | 23 +++++++++++++++++++
 .../X64/PeiSnpSystemRamValidate.c             |  5 ++++
 OvmfPkg/Sec/AmdSev.c                          | 20 +++++++++++++++-
 OvmfPkg/Sec/SecMain.c                         |  7 ++++++
 OvmfPkg/FvmainCompactScratchEnd.fdf.inc       |  5 ++++
 8 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 41fffd6d3bd9..d040ee02b94f 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -358,6 +358,11 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedStart|0x0|UINT32|0x56
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedEnd|0x0|UINT32|0x57
 
+  ## The range of memory that need to be pre-validated in the SEC phase
+  #  when SEV-SNP is active in the guest VM.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedStart|0|UINT32|0x58
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd|0|UINT32|0x59
+
 [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 f4058911e7b6..2b60920f4b25 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
@@ -58,5 +58,7 @@ [FeaturePcd]
 
 [FixedPcd]
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedStart
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedStart
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 9523a8ea6c8f..7e2668ff2f66 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.PcdOvmfSnpSecPreValidatedStart
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
diff --git a/OvmfPkg/Sec/AmdSev.h b/OvmfPkg/Sec/AmdSev.h
index adad96d23189..33af32b9925b 100644
--- a/OvmfPkg/Sec/AmdSev.h
+++ b/OvmfPkg/Sec/AmdSev.h
@@ -69,4 +69,27 @@ SevEsIsEnabled (
   VOID
   );
 
+/**
+ Pre-validate System RAM used for decompressing the PEI and DXE firmware volumes
+ when SEV-SNP is active. The PCDs SecPreValidatedStart and SecPreValidatedEnd are
+ set in OvmfPkg/FvmainCompactScratchEnd.fdf.inc.
+
+**/
+VOID
+SevSnpSecPreValidateSystemRam (
+  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 69ffb79633c4..253d42073907 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
@@ -27,6 +27,11 @@ STATIC SNP_PRE_VALIDATED_RANGE mPreValidatedRange[] = {
   {
     FixedPcdGet32 (PcdOvmfSnpHypervisorPreValidatedStart),
     FixedPcdGet32 (PcdOvmfSnpHypervisorPreValidatedEnd)
+  },
+  // This range is pre-validated by the Sec/SecMain.c
+  {
+    FixedPcdGet32 (PcdOvmfSnpSecPreValidatedStart),
+    FixedPcdGet32 (PcdOvmfSnpSecPreValidatedEnd)
   }
 };
 
diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c
index 054f19216f1e..a626dc3943fe 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
@@ -247,3 +246,22 @@ SevEsIsEnabled (
 
   return (SevEsWorkArea->SevEsEnabled != 0);
 }
+
+/**
+ Pre-validate System RAM used for decompressing the PEI and DXE firmware volumes
+ when SEV-SNP is active. The PCDs SecPreValidatedStart and SecPreValidatedEnd are
+ set in OvmfPkg/FvmainCompactScratchEnd.fdf.inc.
+
+**/
+VOID
+SevSnpSecPreValidateSystemRam (
+  VOID
+  )
+{
+  PHYSICAL_ADDRESS        Start, End;
+
+  Start = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdOvmfSnpSecPreValidatedStart);
+  End = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdOvmfSnpSecPreValidatedEnd);
+
+  MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES (End - Start));
+}
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 406e3a25d0cd..0d80494b062c 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -847,6 +847,13 @@ SecCoreStartupWithStack (
   SecCoreData.BootFirmwareVolumeBase = BootFv;
   SecCoreData.BootFirmwareVolumeSize = (UINTN) BootFv->FvLength;
 
+  if (SevSnpIsEnabled ()) {
+    //
+    // Pre-validate the System RAM used in the SEC Phase
+    //
+    SevSnpSecPreValidateSystemRam ();
+  }
+
   //
   // 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..b560fb0b8e4f 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.PcdOvmfSnpSecPreValidatedStart = $(MEMFD_BASE_ADDRESS) + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
+SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd = $(DECOMP_SCRATCH_BASE) + $(DECOMP_SCRATCH_SIZE)
-- 
2.17.1