linux-kernel - [PATCH v4 14/14] x86/sev: Enable Secure TSC for SNP guests

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Date:   Mon, 14 Aug 2023 11:22:22 +0530
From:   Nikunj A Dadhania <nikunj@....com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <bp@...en8.de>, <thomas.lendacky@....com>,
        <dionnaglaze@...gle.com>, <pgonda@...gle.com>, <seanjc@...gle.com>,
        <pbonzini@...hat.com>, <nikunj@....com>
Subject: [PATCH v4 14/14] x86/sev: Enable Secure TSC for SNP guests

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@....com>
---
 arch/x86/boot/compressed/sev.c |  2 +-
 arch/x86/mm/mem_encrypt.c      | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 014b89c89088..11f951caf2de 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -313,7 +313,7 @@ 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/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");
 }
-- 
2.34.1