x86, microcode, AMD: Add a vendor-specific exit function

This will be used to do cleanup work before the driver exits.
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>

arch/x86/include/asm/microcode.h

@@ -48,6 +48,7 @@ static inline struct microcode_ops * __init init_intel_microcode(void)
 
 #ifdef CONFIG_MICROCODE_AMD
 extern struct microcode_ops * __init init_amd_microcode(void);
+extern void __exit exit_amd_microcode(void);
 
 static inline void get_ucode_data(void *to, const u8 *from, size_t n)
 {
@@ -59,6 +60,7 @@ static inline struct microcode_ops * __init init_amd_microcode(void)
 {
 	return NULL;
 }
+static inline void __exit exit_amd_microcode(void) {}
 #endif
 
 #endif /* _ASM_X86_MICROCODE_H */

arch/x86/kernel/microcode_amd.c

@@ -353,3 +353,7 @@ struct microcode_ops * __init init_amd_microcode(void)
 {
 	return &microcode_amd_ops;
 }
+
+void __exit exit_amd_microcode(void)
+{
+}

arch/x86/kernel/microcode_core.c

@@ -563,6 +563,8 @@ module_init(microcode_init);
 
 static void __exit microcode_exit(void)
 {
+	struct cpuinfo_x86 *c = &cpu_data(0);
+
 	microcode_dev_exit();
 
 	unregister_hotcpu_notifier(&mc_cpu_notifier);
@@ -580,6 +582,9 @@ static void __exit microcode_exit(void)
 
 	microcode_ops = NULL;
 
+	if (c->x86_vendor == X86_VENDOR_AMD)
+		exit_amd_microcode();
+
 	pr_info("Microcode Update Driver: v" MICROCODE_VERSION " removed.\n");
 }
 module_exit(microcode_exit);