[RFC PATCH v4 10/27] OvmfPkg/MemEncryptSevLib: add MemEncryptSevSnpEnabled()

["Brijesh Singh" <brijesh.singh@amd.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

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

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: Laszlo Ersek <lersek@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/Include/Library/MemEncryptSevLib.h    | 12 +++++++++
 .../DxeMemEncryptSevLibInternal.c             | 27 +++++++++++++++++++
 .../PeiMemEncryptSevLibInternal.c             | 27 +++++++++++++++++++
 .../SecMemEncryptSevLibInternal.c             | 19 +++++++++++++
 4 files changed, 85 insertions(+)

diff --git a/OvmfPkg/Include/Library/MemEncryptSevLib.h b/OvmfPkg/Include/Library/MemEncryptSevLib.h
index 76d06c206c8b..2425d8ba0a36 100644
--- a/OvmfPkg/Include/Library/MemEncryptSevLib.h
+++ b/OvmfPkg/Include/Library/MemEncryptSevLib.h
@@ -66,6 +66,18 @@ typedef enum {
   MemEncryptSevAddressRangeError,
 } MEM_ENCRYPT_SEV_ADDRESS_RANGE_STATE;
 
+/**
+  Returns a boolean to indicate whether SEV-SNP is enabled
+
+  @retval TRUE           SEV-SNP is enabled
+  @retval FALSE          SEV-SNP is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevSnpIsEnabled (
+  VOID
+  );
+
 /**
   Returns a boolean to indicate whether SEV-ES is enabled.
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
index 2816f859a0c4..057129723824 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
@@ -19,6 +19,7 @@
 
 STATIC BOOLEAN mSevStatus = FALSE;
 STATIC BOOLEAN mSevEsStatus = FALSE;
+STATIC BOOLEAN mSevSnpStatus = FALSE;
 STATIC BOOLEAN mSevStatusChecked = FALSE;
 
 STATIC UINT64  mSevEncryptionMask = 0;
@@ -82,11 +83,37 @@ InternalMemEncryptSevStatus (
     if (Msr.Bits.SevEsBit) {
       mSevEsStatus = TRUE;
     }
+
+    //
+    // Check MSR_0xC0010131 Bit 2 (Sev-Snp Enabled)
+    //
+    if (Msr.Bits.SevSnpBit) {
+      mSevSnpStatus = TRUE;
+    }
   }
 
   mSevStatusChecked = TRUE;
 }
 
+/**
+  Returns a boolean to indicate whether SEV-SNP is enabled.
+
+  @retval TRUE           SEV-SNP is enabled
+  @retval FALSE          SEV-SNP is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevSnpIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevSnpStatus;
+}
+
 /**
   Returns a boolean to indicate whether SEV-ES is enabled.
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
index e2fd109d120f..b561f211f577 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
@@ -19,6 +19,7 @@
 
 STATIC BOOLEAN mSevStatus = FALSE;
 STATIC BOOLEAN mSevEsStatus = FALSE;
+STATIC BOOLEAN mSevSnpStatus = FALSE;
 STATIC BOOLEAN mSevStatusChecked = FALSE;
 
 STATIC UINT64  mSevEncryptionMask = 0;
@@ -82,11 +83,37 @@ InternalMemEncryptSevStatus (
     if (Msr.Bits.SevEsBit) {
       mSevEsStatus = TRUE;
     }
+
+    //
+    // Check MSR_0xC0010131 Bit 2 (Sev-Snp Enabled)
+    //
+    if (Msr.Bits.SevSnpBit) {
+      mSevSnpStatus = TRUE;
+    }
   }
 
   mSevStatusChecked = TRUE;
 }
 
+/**
+  Returns a boolean to indicate whether SEV-SNP is enabled.
+
+  @retval TRUE           SEV-SNP is enabled
+  @retval FALSE          SEV-SNP is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevSnpIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevSnpStatus;
+}
+
 /**
   Returns a boolean to indicate whether SEV-ES is enabled.
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
index 56d8f3f3183f..69852779e2ff 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
@@ -62,6 +62,25 @@ InternalMemEncryptSevStatus (
   return ReadSevMsr ? AsmReadMsr32 (MSR_SEV_STATUS) : 0;
 }
 
+/**
+  Returns a boolean to indicate whether SEV-SNP is enabled.
+
+  @retval TRUE           SEV-SNP is enabled
+  @retval FALSE          SEV-SNP is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevSnpIsEnabled (
+  VOID
+  )
+{
+  MSR_SEV_STATUS_REGISTER           Msr;
+
+  Msr.Uint32 = InternalMemEncryptSevStatus ();
+
+  return Msr.Bits.SevSnpBit ? TRUE : FALSE;
+}
+
 /**
   Returns a boolean to indicate whether SEV-ES is enabled.
 
-- 
2.17.1