[RFC PATCH v4 17/27] 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: 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                           |  5 ++++
 .../PeiMemEncryptSevLib.inf                   |  2 ++
 OvmfPkg/Sec/SecMain.inf                       |  3 +++
 .../X64/PeiSnpSystemRamValidate.c             |  5 ++++
 OvmfPkg/Sec/SecMain.c                         | 27 +++++++++++++++++++
 OvmfPkg/FvmainCompactScratchEnd.fdf.inc       |  5 ++++
 6 files changed, 47 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index d0ec14ca2318..afc559d74335 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -339,6 +339,11 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedStart|0x0|UINT32|0x51
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedEnd|0x0|UINT32|0x52
 
+  ## 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|0x53
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd|0|UINT32|0x54
+
 [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 7f78dcee2772..8144b1d115cf 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -50,6 +50,7 @@ [LibraryClasses]
   PeCoffExtraActionLib
   ExtractGuidedSectionLib
   LocalApicLib
+  MemEncryptSevLib
   CpuExceptionHandlerLib
 
 [Ppis]
@@ -70,6 +71,8 @@ [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedStart
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
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/SecMain.c b/OvmfPkg/Sec/SecMain.c
index c10441ddf472..f949a9b0349e 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -915,6 +915,26 @@ SevEsIsEnabled (
   return ((SevEsWorkArea != NULL) && (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.
+
+**/
+STATIC
+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));
+}
+
 VOID
 EFIAPI
 SecCoreStartupWithStack (
@@ -1046,6 +1066,13 @@ 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