x86/mm: Add Secure Encrypted Virtualization (SEV) support

Provide support for Secure Encrypted Virtualization (SEV). This initial
support defines a flag that is used by the kernel to determine if it is
running with SEV active.

Signed-off-by: Tom Lendacky <[e-mail]>
Signed-off-by: Brijesh Singh <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Borislav Petkov <[e-mail]>
Tested-by: Borislav Petkov <[e-mail]>
Cc: [e-mail]
Cc: Borislav Petkov <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]

arch/x86/include/asm/mem_encrypt.h

···
 
 void swiotlb_set_mem_attributes(void *vaddr, unsigned long size);
 
+bool sme_active(void);
+bool sev_active(void);
+
 #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
 #define sme_me_mask	0ULL
···
 
 static inline void __init sme_encrypt_kernel(void) { }
 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; }
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */
 

arch/x86/mm/mem_encrypt.c

···
 u64 sme_me_mask __section(.data) = 0;
 EXPORT_SYMBOL_GPL(sme_me_mask);
 
+static bool sev_enabled __section(.data);
+
 /* Buffer used for early in-place encryption by BSP, no locking needed */
 static char sme_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
 
···
 	for (i = 0; i < ARRAY_SIZE(protection_map); i++)
 		protection_map[i] = pgprot_encrypted(protection_map[i]);
 }
+
+/*
+ * SME and SEV are very similar but they are not the same, so there are
+ * times that the kernel will need to distinguish between SME and SEV. The
+ * sme_active() and sev_active() functions are used for this.  When a
+ * distinction isn't needed, the mem_encrypt_active() function can be used.
+ *
+ * The trampoline code is a good example for this requirement.  Before
+ * paging is activated, SME will access all memory as decrypted, but SEV
+ * will access all memory as encrypted.  So, when APs are being brought
+ * up under SME the trampoline area cannot be encrypted, whereas under SEV
+ * the trampoline area must be encrypted.
+ */
+bool sme_active(void)
+{
+	return sme_me_mask && !sev_enabled;
+}
+EXPORT_SYMBOL_GPL(sme_active);
+
+bool sev_active(void)
+{
+	return sme_me_mask && sev_enabled;
+}
+EXPORT_SYMBOL_GPL(sev_active);
 
 /* Architecture __weak replacement functions */
 void __init mem_encrypt_init(void)

include/linux/mem_encrypt.h

···
 
 #define sme_me_mask	0ULL
 
+static inline bool sme_active(void) { return false; }
+static inline bool sev_active(void) { return false; }
+
 #endif	/* CONFIG_ARCH_HAS_MEM_ENCRYPT */
 
-static inline bool sme_active(void)
+static inline bool mem_encrypt_active(void)
 {
-	return !!sme_me_mask;
+	return sme_me_mask;
 }
 
 static inline u64 sme_get_me_mask(void)