[edk2-devel] [PATCH RFC v2 24/28] OvmfPkg/SecMain: Pre-validate the memory used for decompressing Fv

[Brijesh Singh]

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 at linux.ibm.com>
Cc: Min Xu <min.m.xu at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Laszlo Ersek <lersek at redhat.com>
Cc: Erdem Aktas <erdemaktas at google.com>
Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
---
 OvmfPkg/FvmainCompactScratchEnd.fdf.inc                            |  5 ++++
 OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf       |  2 ++
 OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c |  5 ++++
 OvmfPkg/OvmfPkg.dec                                                |  5 ++++
 OvmfPkg/Sec/SecMain.c                                              | 27 ++++++++++++++++++++
 OvmfPkg/Sec/SecMain.inf                                            |  3 +++
 6 files changed, 47 insertions(+)

diff --git a/OvmfPkg/FvmainCompactScratchEnd.fdf.inc b/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
index 46f5258329..b560fb0b8e 100644
--- a/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
+++ b/OvmfPkg/FvmainCompactScratchEnd.fdf.inc
@@ -63,3 +63,8 @@ DEFINE DECOMP_SCRATCH_BASE_MASK      = 0xFFF00000
 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)
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
index f4058911e7..2b60920f4b 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLib.inf
@@ -58,5 +58,7 @@
 
 [FixedPcd]
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedStart
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedStart
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
index ff4c0742ed..7d8e681acd 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/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 70948ab478..d1bfe49731 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -332,6 +332,11 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedStart|0x0|UINT32|0x49
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpHypervisorPreValidatedEnd|0x0|UINT32|0x50
 
+  ## 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|0x51
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd|0|UINT32|0x52
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 7c9650ba8f..c5467465ab 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -907,6 +907,26 @@ 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)(UINTN) PcdGet32 (PcdOvmfSnpSecPreValidatedStart);
+  End = (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSnpSecPreValidatedEnd);
+
+  MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES (End - Start));
+}
+
 VOID
 EFIAPI
 SecCoreStartupWithStack (
@@ -1038,6 +1058,13 @@ 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/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 7f78dcee27..8144b1d115 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -50,6 +50,7 @@
   PeCoffExtraActionLib
   ExtractGuidedSectionLib
   LocalApicLib
+  MemEncryptSevLib
   CpuExceptionHandlerLib
 
 [Ppis]
@@ -70,6 +71,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedStart
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecPreValidatedEnd
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
-- 
2.17.1



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