[PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

["Roth, Michael" <Michael.Roth@amd.com>]

The SEV-SNP Confidential Computing blob contains metadata that should
remain accessible for the life of the guest. Allocate it as
EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
operating system later.

Reported-by: Dov Murik <dovmurik@linux.ibm.com>
Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 14 deletions(-)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 662d3c4ccb..8dfda961d7 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -21,15 +21,36 @@
 #include <Guid/ConfidentialComputingSevSnpBlob.h>
 #include <Library/PcdLib.h>
 
-STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
-  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
-  1,
-  0,
-  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
-  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
-  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
-  FixedPcdGet32 (PcdOvmfCpuidSize),
-};
+STATIC
+EFI_STATUS
+AllocateConfidentialComputingBlob (
+  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
+  )
+{
+  EFI_STATUS                                Status;
+  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
+
+  Status = gBS->AllocatePool (
+                  EfiACPIReclaimMemory,
+                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
+                  (VOID **)&CcBlob
+                  );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
+  CcBlob->Version                = 1;
+  CcBlob->Reserved1              = 0;
+  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
+  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
+  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
+  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
+
+  *CcBlobPtr = CcBlob;
+
+  return EFI_SUCCESS;
+}
 
 EFI_STATUS
 EFIAPI
@@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
   IN EFI_SYSTEM_TABLE  *SystemTable
   )
 {
-  EFI_STATUS                       Status;
-  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
-  UINTN                            NumEntries;
-  UINTN                            Index;
+  EFI_STATUS                                Status;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
+  UINTN                                     NumEntries;
+  UINTN                                     Index;
+  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
 
   //
   // Do nothing when SEV is not enabled
@@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
     }
   }
 
+  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a: AllocateConfidentialComputingBlob(): %r\n",
+      __FUNCTION__,
+      Status
+      ));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+
   //
   // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
   // It contains the location for both the Secrets and CPUID page.
@@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
   if (MemEncryptSevSnpIsEnabled ()) {
     return gBS->InstallConfigurationTable (
                   &gConfidentialComputingSevSnpBlobGuid,
-                  &mSnpBootDxeTable
+                  SnpBootDxeTable
                   );
   }
 
-- 
2.25.1