x86/mm: Extend cc_attr to include AMD SEV-SNP

The CC_ATTR_GUEST_SEV_SNP can be used by the guest to query whether the SNP (Secure Nested Paging) feature is active. Signed-off-by: Brijesh Singh <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Link: https://lore.kernel.org/r/[email protected]
ambv · Apr 6, 2022 · f742b90 · f742b90
1 parent bcce829
commit f742b90
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Showing 4 changed files with 17 additions and 0 deletions.
diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
@@ -57,6 +57,9 @@ static bool amd_cc_platform_has(enum cc_attr attr)
 		return (sev_status & MSR_AMD64_SEV_ENABLED) &&
 			!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
 
+	case CC_ATTR_GUEST_SEV_SNP:
+		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
+
 	default:
 		return false;
 	}

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
@@ -502,8 +502,10 @@
 #define MSR_AMD64_SEV			0xc0010131
 #define MSR_AMD64_SEV_ENABLED_BIT	0
 #define MSR_AMD64_SEV_ES_ENABLED_BIT	1
+#define MSR_AMD64_SEV_SNP_ENABLED_BIT	2
 #define MSR_AMD64_SEV_ENABLED		BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
 #define MSR_AMD64_SEV_ES_ENABLED	BIT_ULL(MSR_AMD64_SEV_ES_ENABLED_BIT)
+#define MSR_AMD64_SEV_SNP_ENABLED	BIT_ULL(MSR_AMD64_SEV_SNP_ENABLED_BIT)
 
 #define MSR_AMD64_VIRT_SPEC_CTRL	0xc001011f
 

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
@@ -62,6 +62,10 @@ static void print_mem_encrypt_feature_info(void)
 	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");
 }
 

diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
@@ -72,6 +72,14 @@ enum cc_attr {
 	 * Examples include TDX guest & SEV.
 	 */
 	CC_ATTR_GUEST_UNROLL_STRING_IO,
+
+	/**
+	 * @CC_ATTR_SEV_SNP: Guest SNP is active.
+	 *
+	 * The platform/OS is running as a guest/virtual machine and actively
+	 * using AMD SEV-SNP features.
+	 */
+	CC_ATTR_GUEST_SEV_SNP,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM