[PATCH v6 39/76] x86/sev-es: Add SEV-ES Feature Detection

[Joerg Roedel]

From: Joerg Roedel <jroedel@xxxxxxx>

Add the sev_es_active function for checking whether SEV-ES is enabled.
Also cache the value of MSR_AMD64_SEV at boot to speed up the feature
checking in the running code.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200724160336.5435-39-joro@xxxxxxxxxx
---
 arch/x86/include/asm/mem_encrypt.h | 3 +++
 arch/x86/include/asm/msr-index.h   | 2 ++
 arch/x86/mm/mem_encrypt.c          | 9 ++++++++-
 arch/x86/mm/mem_encrypt_identity.c | 3 +++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 5049f6c22683..4e72b73a9cb5 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -19,6 +19,7 @@
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 
 extern u64 sme_me_mask;
+extern u64 sev_status;
 extern bool sev_enabled;
 
 void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
@@ -50,6 +51,7 @@ void __init mem_encrypt_init(void);
 
 bool sme_active(void);
 bool sev_active(void);
+bool sev_es_active(void);
 
 #define __bss_decrypted __attribute__((__section__(".bss..decrypted")))
 
@@ -72,6 +74,7 @@ static inline void __init sme_enable(struct boot_params *bp) { }
 
 static inline bool sme_active(void) { return false; }
 static inline bool sev_active(void) { return false; }
+static inline bool sev_es_active(void) { return false; }
 
 static inline int __init
 early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index cd6d651ff730..95871defba91 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -469,7 +469,9 @@
 #define MSR_AMD64_SEV_ES_GHCB		0xc0010130
 #define MSR_AMD64_SEV			0xc0010131
 #define MSR_AMD64_SEV_ENABLED_BIT	0
+#define MSR_AMD64_SEV_ES_ENABLED_BIT	1
 #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_VIRT_SPEC_CTRL	0xc001011f
 
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 9f1177edc2e7..232d6e1bcfc6 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -38,6 +38,7 @@
  * section is later cleared.
  */
 u64 sme_me_mask __section(.data) = 0;
+u64 sev_status __section(.data) = 0;
 EXPORT_SYMBOL(sme_me_mask);
 DEFINE_STATIC_KEY_FALSE(sev_enable_key);
 EXPORT_SYMBOL_GPL(sev_enable_key);
@@ -347,7 +348,13 @@ bool sme_active(void)
 
 bool sev_active(void)
 {
-	return sme_me_mask && sev_enabled;
+	return !!(sev_status & MSR_AMD64_SEV_ENABLED);
+}
+
+/* Needs to be called from non-instrumentable code */
+bool noinstr sev_es_active(void)
+{
+	return !!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
 }
 
 /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index e2b0e2ac07bb..68d75379e06a 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -540,6 +540,9 @@ void __init sme_enable(struct boot_params *bp)
 		if (!(msr & MSR_AMD64_SEV_ENABLED))
 			return;
 
+		/* Save SEV_STATUS to avoid reading MSR again */
+		sev_status = msr;
+
 		/* SEV state cannot be controlled by a command line option */
 		sme_me_mask = me_mask;
 		sev_enabled = true;
-- 
2.28.0