x86/mm: Hide mm_free_global_asid() definition under CONFIG_BROADCAST_TLB_FLUSH

When CONFIG_BROADCAST_TLB_FLUSH is not enabled, mm_free_global_asid() remains
a globally visible symbol and generates a useless function call to it in
destroy_context(). Therefore, hide the mm_free_global_asid() definition under
CONFIG_BROADCAST_TLB_FLUSH and provide a static inline empty version when it
is not enabled to remove the function call.

Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Link: https://patch.msgid.link/b262a8ec8076fb26bb692aaf113848b1e6f40e40.1768448079.git.houwenlong.hwl@antgroup.com

Author: bysui

arch/x86/include/asm/mmu_context.h

@@ -139,9 +139,7 @@ static inline void mm_reset_untag_mask(struct mm_struct *mm)
 #define enter_lazy_tlb enter_lazy_tlb
 extern void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk);
 
-#define mm_init_global_asid mm_init_global_asid
 extern void mm_init_global_asid(struct mm_struct *mm);
-
 extern void mm_free_global_asid(struct mm_struct *mm);
 
 /*

arch/x86/include/asm/tlbflush.h

@@ -292,9 +292,12 @@ static inline bool mm_in_asid_transition(struct mm_struct *mm)
 
 	return mm && READ_ONCE(mm->context.asid_transition);
 }
+
+extern void mm_free_global_asid(struct mm_struct *mm);
 #else
 static inline u16 mm_global_asid(struct mm_struct *mm) { return 0; }
 static inline void mm_init_global_asid(struct mm_struct *mm) { }
+static inline void mm_free_global_asid(struct mm_struct *mm) { }
 static inline void mm_assign_global_asid(struct mm_struct *mm, u16 asid) { }
 static inline void mm_clear_asid_transition(struct mm_struct *mm) { }
 static inline bool mm_in_asid_transition(struct mm_struct *mm) { return false; }

arch/x86/mm/tlb.c

@@ -401,6 +401,7 @@ static void use_global_asid(struct mm_struct *mm)
 	mm_assign_global_asid(mm, asid);
 }
 
+#ifdef CONFIG_BROADCAST_TLB_FLUSH
 void mm_free_global_asid(struct mm_struct *mm)
 {
 	if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
@@ -412,13 +413,12 @@ void mm_free_global_asid(struct mm_struct *mm)
 	guard(raw_spinlock_irqsave)(&global_asid_lock);
 
 	/* The global ASID can be re-used only after flush at wrap-around. */
-#ifdef CONFIG_BROADCAST_TLB_FLUSH
 	__set_bit(mm->context.global_asid, global_asid_freed);
 
 	mm->context.global_asid = 0;
 	global_asid_available++;
-#endif
 }
+#endif
 
 /*
  * Is the mm transitioning from a CPU-local ASID to a global ASID?