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[PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU

Kevin Brodsky posted 13 patches 2 weeks, 1 day ago
There is a newer version of this series
[PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU
Posted by Kevin Brodsky 2 weeks, 1 day ago 
Architectures currently opt in for implementing lazy_mmu helpers by
defining __HAVE_ARCH_ENTER_LAZY_MMU_MODE.

In preparation for introducing a generic lazy_mmu layer that will
require storage in task_struct, let's switch to a cleaner approach:
instead of defining a macro, select a CONFIG option.

This patch introduces CONFIG_ARCH_LAZY_MMU and has each arch select
it when it implements lazy_mmu helpers.
__HAVE_ARCH_ENTER_LAZY_MMU_MODE is removed and <linux/pgtable.h>
relies on the new CONFIG instead.

On x86, lazy_mmu helpers are only implemented if PARAVIRT_XXL is
selected. This creates some complications in arch/x86/boot/, because
a few files manually undefine PARAVIRT* options. As a result
<asm/paravirt.h> does not define the lazy_mmu helpers, but this
breaks the build as <linux/pgtable.h> only defines them if
!CONFIG_ARCH_LAZY_MMU. There does not seem to be a clean way out of
this - let's just undefine that new CONFIG too.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
 arch/arm64/Kconfig                                 | 1 +
 arch/arm64/include/asm/pgtable.h                   | 1 -
 arch/powerpc/include/asm/book3s/64/tlbflush-hash.h | 2 --
 arch/powerpc/platforms/Kconfig.cputype             | 1 +
 arch/sparc/Kconfig                                 | 1 +
 arch/sparc/include/asm/tlbflush_64.h               | 2 --
 arch/x86/Kconfig                                   | 1 +
 arch/x86/boot/compressed/misc.h                    | 1 +
 arch/x86/boot/startup/sme.c                        | 1 +
 arch/x86/include/asm/paravirt.h                    | 1 -
 include/linux/pgtable.h                            | 2 +-
 mm/Kconfig                                         | 3 +++
 12 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6663ffd23f25..12d47a5f5e56 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -122,6 +122,7 @@ config ARM64
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
 	select ARCH_HAS_UBSAN
+	select ARCH_LAZY_MMU
 	select ARM_AMBA
 	select ARM_ARCH_TIMER
 	select ARM_GIC
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index aa89c2e67ebc..e3cbb10288c4 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -80,7 +80,6 @@ static inline void queue_pte_barriers(void)
 	}
 }
 
-#define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	/*
diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
index 7704dbe8e88d..623a8a8b2d0e 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
@@ -24,8 +24,6 @@ DECLARE_PER_CPU(struct ppc64_tlb_batch, ppc64_tlb_batch);
 
 extern void __flush_tlb_pending(struct ppc64_tlb_batch *batch);
 
-#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
-
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	struct ppc64_tlb_batch *batch;
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 7b527d18aa5e..a5e06aaf19cd 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -93,6 +93,7 @@ config PPC_BOOK3S_64
 	select IRQ_WORK
 	select PPC_64S_HASH_MMU if !PPC_RADIX_MMU
 	select KASAN_VMALLOC if KASAN
+	select ARCH_LAZY_MMU
 
 config PPC_BOOK3E_64
 	bool "Embedded processors"
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index a630d373e645..59f17996a353 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -112,6 +112,7 @@ config SPARC64
 	select NEED_PER_CPU_PAGE_FIRST_CHUNK
 	select ARCH_SUPPORTS_SCHED_SMT if SMP
 	select ARCH_SUPPORTS_SCHED_MC  if SMP
+	select ARCH_LAZY_MMU
 
 config ARCH_PROC_KCORE_TEXT
 	def_bool y
diff --git a/arch/sparc/include/asm/tlbflush_64.h b/arch/sparc/include/asm/tlbflush_64.h
index 925bb5d7a4e1..4e1036728e2f 100644
--- a/arch/sparc/include/asm/tlbflush_64.h
+++ b/arch/sparc/include/asm/tlbflush_64.h
@@ -39,8 +39,6 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
 
 void flush_tlb_kernel_range(unsigned long start, unsigned long end);
 
-#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
-
 void flush_tlb_pending(void);
 void arch_enter_lazy_mmu_mode(void);
 void arch_flush_lazy_mmu_mode(void);
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fa3b616af03a..85de037cad8c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -804,6 +804,7 @@ config PARAVIRT
 config PARAVIRT_XXL
 	bool
 	depends on X86_64
+	select ARCH_LAZY_MMU
 
 config PARAVIRT_DEBUG
 	bool "paravirt-ops debugging"
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index db1048621ea2..80b3b79a1001 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -11,6 +11,7 @@
 #undef CONFIG_PARAVIRT
 #undef CONFIG_PARAVIRT_XXL
 #undef CONFIG_PARAVIRT_SPINLOCKS
+#undef CONFIG_ARCH_LAZY_MMU
 #undef CONFIG_KASAN
 #undef CONFIG_KASAN_GENERIC
 
diff --git a/arch/x86/boot/startup/sme.c b/arch/x86/boot/startup/sme.c
index e7ea65f3f1d6..af74d09b68bc 100644
--- a/arch/x86/boot/startup/sme.c
+++ b/arch/x86/boot/startup/sme.c
@@ -24,6 +24,7 @@
 #undef CONFIG_PARAVIRT
 #undef CONFIG_PARAVIRT_XXL
 #undef CONFIG_PARAVIRT_SPINLOCKS
+#undef CONFIG_ARCH_LAZY_MMU
 
 /*
  * This code runs before CPU feature bits are set. By default, the
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index b5e59a7ba0d0..13f9cd31c8f8 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -526,7 +526,6 @@ static inline void arch_end_context_switch(struct task_struct *next)
 	PVOP_VCALL1(cpu.end_context_switch, next);
 }
 
-#define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	PVOP_VCALL0(mmu.lazy_mode.enter);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 32e8457ad535..124d5fa2975f 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -231,7 +231,7 @@ static inline int pmd_dirty(pmd_t pmd)
  * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
  * and the mode cannot be used in interrupt context.
  */
-#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
+#ifndef CONFIG_ARCH_LAZY_MMU
 static inline void arch_enter_lazy_mmu_mode(void) {}
 static inline void arch_leave_lazy_mmu_mode(void) {}
 static inline void arch_flush_lazy_mmu_mode(void) {}
diff --git a/mm/Kconfig b/mm/Kconfig
index 0e26f4fc8717..2fdcb42ca1a1 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1372,6 +1372,9 @@ config PT_RECLAIM
 config FIND_NORMAL_PAGE
 	def_bool n
 
+config ARCH_LAZY_MMU
+	bool
+
 source "mm/damon/Kconfig"
 
 endmenu
-- 
2.47.0
Re: [PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU
Posted by Mike Rapoport 1 week, 5 days ago 
On Wed, Oct 15, 2025 at 09:27:19AM +0100, Kevin Brodsky wrote:
> Architectures currently opt in for implementing lazy_mmu helpers by
> defining __HAVE_ARCH_ENTER_LAZY_MMU_MODE.
> 
> In preparation for introducing a generic lazy_mmu layer that will
> require storage in task_struct, let's switch to a cleaner approach:
> instead of defining a macro, select a CONFIG option.
> 
> This patch introduces CONFIG_ARCH_LAZY_MMU and has each arch select
> it when it implements lazy_mmu helpers.
> __HAVE_ARCH_ENTER_LAZY_MMU_MODE is removed and <linux/pgtable.h>
> relies on the new CONFIG instead.
> 
> On x86, lazy_mmu helpers are only implemented if PARAVIRT_XXL is
> selected. This creates some complications in arch/x86/boot/, because
> a few files manually undefine PARAVIRT* options. As a result
> <asm/paravirt.h> does not define the lazy_mmu helpers, but this
> breaks the build as <linux/pgtable.h> only defines them if
> !CONFIG_ARCH_LAZY_MMU. There does not seem to be a clean way out of
> this - let's just undefine that new CONFIG too.
> 
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> ---

...

> @@ -231,7 +231,7 @@ static inline int pmd_dirty(pmd_t pmd)
>   * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
>   * and the mode cannot be used in interrupt context.
>   */
> -#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
> +#ifndef CONFIG_ARCH_LAZY_MMU
>  static inline void arch_enter_lazy_mmu_mode(void) {}
>  static inline void arch_leave_lazy_mmu_mode(void) {}
>  static inline void arch_flush_lazy_mmu_mode(void) {}
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 0e26f4fc8717..2fdcb42ca1a1 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1372,6 +1372,9 @@ config PT_RECLAIM
>  config FIND_NORMAL_PAGE
>  	def_bool n
>  
> +config ARCH_LAZY_MMU
> +	bool
> +

I think a better name would be ARCH_HAS_LAZY_MMU and the config option fits
better to arch/Kconfig.

>  source "mm/damon/Kconfig"
>  
>  endmenu
> -- 
> 2.47.0
> 

-- 
Sincerely yours,
Mike.
Re: [PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU
Posted by Kevin Brodsky 1 week, 3 days ago 
On 18/10/2025 11:52, Mike Rapoport wrote:
>> @@ -231,7 +231,7 @@ static inline int pmd_dirty(pmd_t pmd)
>>   * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
>>   * and the mode cannot be used in interrupt context.
>>   */
>> -#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
>> +#ifndef CONFIG_ARCH_LAZY_MMU
>>  static inline void arch_enter_lazy_mmu_mode(void) {}
>>  static inline void arch_leave_lazy_mmu_mode(void) {}
>>  static inline void arch_flush_lazy_mmu_mode(void) {}
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index 0e26f4fc8717..2fdcb42ca1a1 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -1372,6 +1372,9 @@ config PT_RECLAIM
>>  config FIND_NORMAL_PAGE
>>  	def_bool n
>>  
>> +config ARCH_LAZY_MMU
>> +	bool
>> +
> I think a better name would be ARCH_HAS_LAZY_MMU and the config option fits
> better to arch/Kconfig.

Sounds fine by me - I'm inclined to make it slightly longer still,
ARCH_HAS_LAZY_MMU_MODE, to avoid making "LAZY_MMU" sound like some HW
feature.

- Kevin
Re: [PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU
Posted by David Hildenbrand 6 days, 23 hours ago 
On 20.10.25 12:37, Kevin Brodsky wrote:
> On 18/10/2025 11:52, Mike Rapoport wrote:
>>> @@ -231,7 +231,7 @@ static inline int pmd_dirty(pmd_t pmd)
>>>    * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
>>>    * and the mode cannot be used in interrupt context.
>>>    */
>>> -#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
>>> +#ifndef CONFIG_ARCH_LAZY_MMU
>>>   static inline void arch_enter_lazy_mmu_mode(void) {}
>>>   static inline void arch_leave_lazy_mmu_mode(void) {}
>>>   static inline void arch_flush_lazy_mmu_mode(void) {}
>>> diff --git a/mm/Kconfig b/mm/Kconfig
>>> index 0e26f4fc8717..2fdcb42ca1a1 100644
>>> --- a/mm/Kconfig
>>> +++ b/mm/Kconfig
>>> @@ -1372,6 +1372,9 @@ config PT_RECLAIM
>>>   config FIND_NORMAL_PAGE
>>>   	def_bool n
>>>   
>>> +config ARCH_LAZY_MMU
>>> +	bool
>>> +
>> I think a better name would be ARCH_HAS_LAZY_MMU and the config option fits
>> better to arch/Kconfig.
> 
> Sounds fine by me - I'm inclined to make it slightly longer still,
> ARCH_HAS_LAZY_MMU_MODE, to avoid making "LAZY_MMU" sound like some HW
> feature.

LGTM.

-- 
Cheers

David / dhildenb

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