linux-kernel - [PATCHv2, RESEND] x86/mm: Fix memory encryption features advertisement

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Date: Wed, 24 Jan 2024 16:02:16 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Dexuan Cui <decui@...rosoft.com>
Subject: [PATCHv2, RESEND] x86/mm: Fix memory encryption features advertisement

When memory encryption is enabled, the kernel prints the encryption
flavor that the system supports.

The check assumes that everything is AMD SME/SEV if it doesn't have
the TDX CPU feature set.

Hyper-V vTOM sets cc_vendor to CC_VENDOR_INTEL when it runs as L2 guest
on top of TDX, but not X86_FEATURE_TDX_GUEST. Hyper-V only needs memory
encryption enabled for I/O without the rest of CoCo enabling.

To avoid confusion, check the cc_vendor directly.

Possible alternative is to completely removing the print statement.
For a regular TDX guest, the kernel already prints a message indicating
that it is booting on TDX. Similarly, AMD and Hyper-V can also display
a message during their enumeration process.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Acked-by: Tom Lendacky <thomas.lendacky@....com>
Acked-by: Kai Huang <kai.huang@...el.com>
Cc: Dexuan Cui <decui@...rosoft.com>
---
 arch/x86/mm/mem_encrypt.c | 56 +++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 26 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index c290c55b632b..d035bce3a2b0 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -42,38 +42,42 @@ bool force_dma_unencrypted(struct device *dev)
 
 static void print_mem_encrypt_feature_info(void)
 {
-	pr_info("Memory Encryption Features active:");
+	pr_info("Memory Encryption Features active: ");
 
-	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
-		pr_cont(" Intel TDX\n");
-		return;
-	}
+	switch (cc_vendor) {
+	case CC_VENDOR_INTEL:
+		pr_cont("Intel TDX\n");
+		break;
+	case CC_VENDOR_AMD:
+		pr_cont("AMD");
 
-	pr_cont(" AMD");
-
-	/* Secure Memory Encryption */
-	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
+		/* Secure Memory Encryption */
+		if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
 		/*
 		 * SME is mutually exclusive with any of the SEV
 		 * features below.
-		 */
-		pr_cont(" SME\n");
-		return;
+		*/
+			pr_cont(" SME\n");
+			return;
+		}
+
+		/* Secure Encrypted Virtualization */
+		if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+			pr_cont(" SEV");
+
+		/* Encrypted Register State */
+		if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+			pr_cont(" SEV-ES");
+
+		/* Secure Nested Paging */
+		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+			pr_cont(" SEV-SNP");
+
+		pr_cont("\n");
+		break;
+	default:
+		pr_cont("Unknown\n");
 	}
-
-	/* Secure Encrypted Virtualization */
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
-		pr_cont(" SEV");
-
-	/* Encrypted Register State */
-	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
-		pr_cont(" SEV-ES");
-
-	/* Secure Nested Paging */
-	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
-		pr_cont(" SEV-SNP");
-
-	pr_cont("\n");
 }
 
 /* Architecture __weak replacement functions */
-- 
2.43.0