[RFC PATCH 11/11] x86/sev: Enable Secure TSC for SNP guests

[Nikunj A Dadhania <nikunj@amd.com>]

Now that all the required plumbing is done for enabling SNP
Secure TSC feature, add Secure TSC to snp features present list.

The CC_ATTR_GUEST_SECURE_TSC can be used by the guest to query whether
the SNP guest has Secure TSC feature active.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 arch/x86/boot/compressed/sev.c |  2 +-
 arch/x86/coco/core.c           |  3 +++
 arch/x86/mm/mem_encrypt.c      | 10 ++++++++--
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index d63ad8f99f83..13b6ff192c3e 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -315,7 +315,7 @@ static void enforce_vmpl0(void)
  * by the guest kernel. As and when a new feature is implemented in the
  * guest kernel, a corresponding bit should be added to the mask.
  */
-#define SNP_FEATURES_PRESENT (0)
+#define SNP_FEATURES_PRESENT (MSR_AMD64_SNP_SECURE_TSC)
 
 void snp_check_features(void)
 {
diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 49b44f881484..a3d93ed722c9 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -68,6 +68,9 @@ static bool amd_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_GUEST_SEV_SNP:
 		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 
+	case CC_ATTR_GUEST_SECURE_TSC:
+		return sev_status & MSR_AMD64_SNP_SECURE_TSC;
+
 	default:
 		return false;
 	}
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 01abecc9a774..26608b9f2ca7 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -69,8 +69,14 @@ static void print_mem_encrypt_feature_info(void)
 		pr_cont(" SEV-ES");
 
 	/* Secure Nested Paging */
-	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
-		pr_cont(" SEV-SNP");
+	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
+		pr_cont(" SEV-SNP\n");
+		pr_cont("SNP Features active: ");
+
+		/* SNP Secure TSC */
+		if (cc_platform_has(CC_ATTR_GUEST_SECURE_TSC))
+			pr_cont(" SECURE-TSC");
+	}
 
 	pr_cont("\n");
 }
-- 
2.32.0