x86/sev: Get rid of special sev_es_enable_key

A SEV-ES guest is active on AMD when CC_ATTR_GUEST_STATE_ENCRYPT is set.
I.e., MSR_AMD64_SEV, bit 1, SEV_ES_Enabled. So no need for a special
static key.

No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230328201712.25852-3-bp@alien8.de

arch/x86/include/asm/sev.h

@@ -14,6 +14,7 @@
 #include <asm/insn.h>
 #include <asm/sev-common.h>
 #include <asm/bootparam.h>
+#include <asm/coco.h>
 
 #define GHCB_PROTOCOL_MIN	1ULL
 #define GHCB_PROTOCOL_MAX	2ULL
@@ -136,24 +137,26 @@ struct snp_secrets_page_layout {
 } __packed;
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
-extern struct static_key_false sev_es_enable_key;
 extern void __sev_es_ist_enter(struct pt_regs *regs);
 extern void __sev_es_ist_exit(void);
 static __always_inline void sev_es_ist_enter(struct pt_regs *regs)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_ist_enter(regs);
 }
 static __always_inline void sev_es_ist_exit(void)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_ist_exit();
 }
 extern int sev_es_setup_ap_jump_table(struct real_mode_header *rmh);
 extern void __sev_es_nmi_complete(void);
 static __always_inline void sev_es_nmi_complete(void)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_nmi_complete();
 }
 extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);

arch/x86/kernel/sev.c

@@ -113,8 +113,6 @@ struct ghcb_state {
 };
 
 static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
-DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);
-
 static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
 
 struct sev_config {
@@ -1395,9 +1393,6 @@ void __init sev_es_init_vc_handling(void)
 			sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
 	}
 
-	/* Enable SEV-ES special handling */
-	static_branch_enable(&sev_es_enable_key);
-
 	/* Initialize per-cpu GHCB pages */
 	for_each_possible_cpu(cpu) {
 		alloc_runtime_data(cpu);