[RFC PATCH v2 02/44] OvmfPkg/MemEncryptSevLib: Add an SEV-ES guest indicator function

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Create a function that can be used to determine if the VM is running
as an SEV-ES guest.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/Include/Library/MemEncryptSevLib.h    | 12 +++
 .../MemEncryptSevLibInternal.c                | 77 ++++++++++++-------
 2 files changed, 62 insertions(+), 27 deletions(-)

diff --git a/OvmfPkg/Include/Library/MemEncryptSevLib.h b/OvmfPkg/Include/Library/MemEncryptSevLib.h
index 64dd6977b0f8..a50a0de9c870 100644
--- a/OvmfPkg/Include/Library/MemEncryptSevLib.h
+++ b/OvmfPkg/Include/Library/MemEncryptSevLib.h
@@ -13,6 +13,18 @@
 
 #include <Base.h>
 
+/**
+  Returns a boolean to indicate whether SEV-ES is enabled
+
+  @retval TRUE           SEV-ES is enabled
+  @retval FALSE          SEV-ES is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsIsEnabled (
+  VOID
+  );
+
 /**
   Returns a boolean to indicate whether SEV is enabled
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
index 96a66e373f11..9c1d68e017fe 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
@@ -20,19 +20,17 @@
 #include <Uefi/UefiBaseType.h>
 
 STATIC BOOLEAN mSevStatus = FALSE;
+STATIC BOOLEAN mSevEsStatus = FALSE;
 STATIC BOOLEAN mSevStatusChecked = FALSE;
 
 /**
 
-  Returns a boolean to indicate whether SEV is enabled
-
-  @retval TRUE           SEV is enabled
-  @retval FALSE          SEV is not enabled
+  Reads and sets the status of SEV features
   **/
 STATIC
-BOOLEAN
+VOID
 EFIAPI
-InternalMemEncryptSevIsEnabled (
+InternalMemEncryptSevStatus (
   VOID
   )
 {
@@ -56,32 +54,57 @@ InternalMemEncryptSevIsEnabled (
       //
       Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
       if (Msr.Bits.SevBit) {
-        return TRUE;
+        mSevStatus = TRUE;
+      }
+
+      if (Eax.Bits.SevEsBit) {
+        //
+        // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled)
+        //
+        if (Msr.Bits.SevEsBit) {
+          mSevEsStatus = TRUE;
+        }
       }
     }
   }
 
-  return FALSE;
-}
-
-/**
-  Returns a boolean to indicate whether SEV is enabled
-
-  @retval TRUE           SEV is enabled
-  @retval FALSE          SEV is not enabled
-**/
-BOOLEAN
-EFIAPI
-MemEncryptSevIsEnabled (
-  VOID
-  )
-{
-  if (mSevStatusChecked) {
-    return mSevStatus;
-  }
-
-  mSevStatus = InternalMemEncryptSevIsEnabled();
   mSevStatusChecked = TRUE;
+}
+
+/**
+  Returns a boolean to indicate whether SEV-ES is enabled
+
+  @retval TRUE           SEV-ES is enabled
+  @retval FALSE          SEV-ES is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus();
+  }
+
+  return mSevEsStatus;
+}
+
+/**
+  Returns a boolean to indicate whether SEV is enabled
+
+  @retval TRUE           SEV is enabled
+  @retval FALSE          SEV is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus();
+  }
 
   return mSevStatus;
 }
-- 
2.17.1