3 files changed, 51 insertions, 1 deletions
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c
index bc891c2636..7797febb8a 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c
@@ -14,6 +14,43 @@
 
 #include "SnpPageStateChange.h"
 
+//
+// The variable used for the VMPL check.
+//
+STATIC UINT8  gVmpl0Data[4096];
+
+/**
+ The function checks whether SEV-SNP guest is booted under VMPL0.
+
+ @retval  TRUE      The guest is booted under VMPL0
+ @retval  FALSE     The guest is not booted under VMPL0
+ **/
+STATIC
+BOOLEAN
+SevSnpIsVmpl0 (
+  VOID
+  )
+{
+  UINT64      Rdx;
+  EFI_STATUS  Status;
+
+  //
+  // There is no straightforward way to query the current VMPL level.
+  // The simplest method is to use the RMPADJUST instruction to change
+  // a page permission to a VMPL level-1, and if the guest kernel is
+  // launched at a level <= 1, then RMPADJUST instruction will return
+  // an error.
+  //
+  Rdx = 1;
+
+  Status = AsmRmpAdjust ((UINT64)gVmpl0Data, 0, Rdx);
+  if (EFI_ERROR (Status)) {
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
 /**
   Pre-validate the system RAM when SEV-SNP is enabled in the guest VM.
 
@@ -32,5 +69,14 @@ MemEncryptSevSnpPreValidateSystemRam (
     return;
   }
 
+  //
+  // The page state change uses the PVALIDATE instruction. The instruction
+  // can be run on VMPL-0 only. If its not VMPL-0 guest then terminate
+  // the boot.
+  //
+  if (!SevSnpIsVmpl0 ()) {
+    SnpPageStateFailureTerminate ();
+  }
+
   InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
 }
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h
index b396f0ffbd..43319cc9ed 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h
@@ -27,4 +27,9 @@ InternalSetPageState (
   IN BOOLEAN               UseLargeEntry
   );
 
+VOID
+SnpPageStateFailureTerminate (
+  VOID
+  );
+
 #endif
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
index 9c552ef5c7..d11aafae84 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
@@ -42,7 +42,6 @@ MemoryStateToGhcbOp (
   return Cmd;
 }
 
-STATIC
 VOID
 SnpPageStateFailureTerminate (
   VOID