[PATCH v9 07/43] x86/mm: Extend cc_attr to include AMD SEV-SNP

Brijesh Singh
2022-01-28T17:18:51Z

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 <brijesh.singh@amd.com>
---
arch/x86/include/asm/msr-index.h | 2 ++
arch/x86/kernel/cc_platform.c | 2 ++
arch/x86/mm/mem_encrypt.c | 4 ++++
include/linux/cc_platform.h | 8 ++++++++
4 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3faf0f97edb1..0b3b4dcf55a7 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -481,8 +481,10 @@
#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/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
index 6a6ffcd978f6..b9d1361d112b 100644
--- a/arch/x86/kernel/cc_platform.c
+++ b/arch/x86/kernel/cc_platform.c
@@ -59,6 +59,8 @@ 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/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 50d209939c66..f85868c031c6 100644
--- 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
index efd8205282da..d08dd65b5c43 100644
--- 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
--
2.25.1