linux-kernel - [PATCH] x86/mm: Hide mm_free_global_asid() definition under 'CONFIG_BROADCAST_TLB

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Message-Id: <f5b5021cd1936127ba73b9d62ff7a975260c70eb.1768396374.git.houwenlong.hwl@antgroup.com>
Date: Wed, 14 Jan 2026 21:21:54 +0800
From: Hou Wenlong <houwenlong.hwl@...group.com>
To: linux-kernel@...r.kernel.org
Cc: Hou Wenlong <houwenlong.hwl@...group.com>,
	Thomas Gleixner <tglx@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...riel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Will Deacon <will@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Jann Horn <jannh@...gle.com>,
	Barry Song <baohua@...nel.org>
Subject: [PATCH] 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@...group.com>
---
 arch/x86/include/asm/mmu_context.h | 5 -----
 arch/x86/include/asm/tlbflush.h    | 3 +++
 arch/x86/mm/tlb.c                  | 4 ++--
 3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 73bf3b1b44e8..fa99293dcd91 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -139,11 +139,6 @@ 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);
-
 /*
  * Init a new mm.  Used on mm copies, like at fork()
  * and on mm's that are brand-new, like at execve().
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 00daedfefc1b..5114bf50c911 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/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; }
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index f5b93e01e347..621e09d049cb 100644
--- a/arch/x86/mm/tlb.c
+++ b/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?
-- 
2.31.1