[PATCH v14 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>
Acked-by: Gerd Hoffmann <kraxel@redhat.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 bc14cf2ed403..c22b846cd663 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -364,6 +364,10 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|0|UINT32|0x60
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize|0|UINT32|0x61
 
+  ## The range of memory that is validated by the SEC phase.
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart|0|UINT32|0x62
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd|0|UINT32|0x63
+
 [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 49d5bd1beff1..50c83859d7e7 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
@@ -60,3 +60,5 @@ [FixedPcd]
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedEnd
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecValidatedStart
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 41dcdba1209a..95cf0025e100 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -52,6 +52,7 @@ [LibraryClasses]
   PeCoffExtraActionLib
   ExtractGuidedSectionLib
   LocalApicLib
+  MemEncryptSevLib
   CpuExceptionHandlerLib
 
 [Ppis]
@@ -74,6 +75,8 @@ [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 c0b1ca96183d..dffd2ceb9656 100644
--- a/OvmfPkg/Sec/AmdSev.h
+++ b/OvmfPkg/Sec/AmdSev.h
@@ -68,4 +68,27 @@ 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 0e3eba3c5121..497016544482 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
@@ -29,6 +29,11 @@ STATIC SNP_PRE_VALIDATED_RANGE  mPreValidatedRange[] = {
     FixedPcdGet32 (PcdOvmfSecPageTablesBase),
     FixedPcdGet32 (PcdOvmfPeiMemFvBase),
   },
+  // 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 aa655fd9cbae..499d0c27d8fa 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
@@ -281,3 +280,24 @@ 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)(UINTN)PcdGet32 (PcdOvmfSecValidatedStart);
+    End   = (EFI_PHYSICAL_ADDRESS)(UINTN)PcdGet32 (PcdOvmfSecValidatedEnd);
+
+    MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES ((UINTN)(End - Start)));
+  }
+}
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 58e3b923b40e..2c5561661ef3 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -860,6 +860,11 @@ 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