linux-kernel - Re: [PATCH v6 RESEND 1/3] x86/mm/tlb: Make enter_lazy

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Message-ID: <20260211153608.78083-1-qq570070308@gmail.com>
Date: Wed, 11 Feb 2026 23:36:08 +0800
From: Xie Yuanbin <qq570070308@...il.com>
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Cc: linux-kernel@...r.kernel.org,
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	Xie Yuanbin <qq570070308@...il.com>
Subject: Re: [PATCH v6 RESEND 1/3] x86/mm/tlb: Make enter_lazy_tlb() always inline on x86

On Tue, 10 Feb 2026 08:07:38 -0800, Dave Hansen wrote:
> On 2/10/26 07:32, Xie Yuanbin wrote:
>> This was just to fix a compilation error:
>> 'cpu_tlbstate' is defined in 'include/asm/tlbflush.h' inside of
>> '#ifndef MODULE'. So if the '#ifndef MODULE' is not added here,
>> the compilation error will be triggered:
>
> Rather than sprinkling #ifdefs and 'cpu_tlbstate' references around,
> could we try to keep them confined to asm/tlbflush.h as much as
> possible, please?
>
> I mean, mmu_context.h _does_ include asm/tlbflush.h, so even if you
> stuck enter_lazy_tlb() in asm/tlbflush.h, everything should keep
> working, no?
>
> That would both prevent adding a random #ifdef and keep 'cpu_tlbstate'
> references limited.

I apologize for misunderstanding your meaning bedore. I tried your
suggestion and there were no compilation warnings or errors:
```patch
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 1acafb1c6a93..ef5b507de34e 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -136,9 +136,6 @@ static inline void mm_reset_untag_mask(struct mm_struct *mm)
 }
 #endif

-#define enter_lazy_tlb enter_lazy_tlb
-extern void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk);
-
 extern void mm_init_global_asid(struct mm_struct *mm);
 extern void mm_free_global_asid(struct mm_struct *mm);

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 5a3cdc439e38..4bc5eb84e135 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -172,6 +172,15 @@ struct tlb_state_shared {
 };
 DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);

+static __always_inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+	if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)
+		return;
+
+	this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
+}
+#define enter_lazy_tlb enter_lazy_tlb
+
 bool nmi_uaccess_okay(void);
 #define nmi_uaccess_okay nmi_uaccess_okay

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 621e09d049cb..55143cbd6cd2 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -984,13 +984,6 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next,
  * in a row.  It will notify us that we're going back to a real mm by
  * calling switch_mm_irqs_off().
  */
-void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-	if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)
-		return;
-
-	this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
-}

 /*
  * Using a temporary mm allows to set temporary mappings that are not accessible
```

However, I'm a little worried that moving
'#define enter_lazy_tlb enter_lazy_tlb' into '#ifndef MODULE' might cause
other issues, so I placed it outside '#ifndef MODULE' outside in my
first patch.

What about this (compilation tested):
```patch
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 1acafb1c6a93..14e776876c69 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -136,8 +136,12 @@ static inline void mm_reset_untag_mask(struct mm_struct *mm)
 }
 #endif

-#define enter_lazy_tlb enter_lazy_tlb
-extern void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk);
+#define enter_lazy_tlb(mm, tsk) \
+	do {								\
+		if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)	\
+			break;						\
+		this_cpu_write(cpu_tlbstate_shared.is_lazy, true);	\
+	} while (0)

 extern void mm_init_global_asid(struct mm_struct *mm);
 extern void mm_free_global_asid(struct mm_struct *mm);
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 621e09d049cb..55143cbd6cd2 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -984,13 +984,6 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next,
  * in a row.  It will notify us that we're going back to a real mm by
  * calling switch_mm_irqs_off().
  */
-void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-	if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)
-		return;
-
-	this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
-}

 /*
  * Using a temporary mm allows to set temporary mappings that are not accessible
```