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_HAS_LAZY_MMU_MODE 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_HAS_LAZY_MMU_MODE. 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..e6bf5c7311b5 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_HAS_LAZY_MMU_MODE
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 0944e296dd4a..54f8d6bb6f22 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..2942d57cf59c 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_HAS_LAZY_MMU_MODE
config PPC_BOOK3E_64
bool "Embedded processors"
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index a630d373e645..2bad14744ca4 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_HAS_LAZY_MMU_MODE
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..ef4332d720ab 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_HAS_LAZY_MMU_MODE
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..cdd7f692d9ee 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_HAS_LAZY_MMU_MODE
#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..b76a7c95dfe1 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_HAS_LAZY_MMU_MODE
/*
* 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..9894366e768b 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_HAS_LAZY_MMU_MODE
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..5480c9a1bfb2 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1372,6 +1372,9 @@ config PT_RECLAIM
config FIND_NORMAL_PAGE
def_bool n
+config ARCH_HAS_LAZY_MMU_MODE
+ bool
+
source "mm/damon/Kconfig"
endmenu
--
2.47.0On 29/10/2025 10:09, 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_HAS_LAZY_MMU_MODE 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_HAS_LAZY_MMU_MODE. 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..e6bf5c7311b5 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_HAS_LAZY_MMU_MODE
nit: This list is mostly in alphabetical order. Further up the list there are a
lot of ARCH_HAS_* entries. Perhaps move it to the correct position in that lot?
Then ARCH_HAS_UBSAN stays out of order on its own.
Otherwise, all looks reasonable to me:
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> 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 0944e296dd4a..54f8d6bb6f22 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..2942d57cf59c 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_HAS_LAZY_MMU_MODE
>
> config PPC_BOOK3E_64
> bool "Embedded processors"
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index a630d373e645..2bad14744ca4 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_HAS_LAZY_MMU_MODE
>
> 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..ef4332d720ab 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_HAS_LAZY_MMU_MODE
>
> 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..cdd7f692d9ee 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_HAS_LAZY_MMU_MODE
> #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..b76a7c95dfe1 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_HAS_LAZY_MMU_MODE
>
> /*
> * 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..9894366e768b 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_HAS_LAZY_MMU_MODE
> 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..5480c9a1bfb2 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1372,6 +1372,9 @@ config PT_RECLAIM
> config FIND_NORMAL_PAGE
> def_bool n
>
> +config ARCH_HAS_LAZY_MMU_MODE
> + bool
> +
> source "mm/damon/Kconfig"
>
> endmenu
On 07/11/2025 13:56, Ryan Roberts wrote: >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 6663ffd23f25..e6bf5c7311b5 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_HAS_LAZY_MMU_MODE > nit: This list is mostly in alphabetical order. Further up the list there are a > lot of ARCH_HAS_* entries. Perhaps move it to the correct position in that lot? > Then ARCH_HAS_UBSAN stays out of order on its own. That's fair, it does look like it's mostly in order apart from ARCH_HAS_UBSAN. Will move it further up. - Kevin
Kevin Brodsky <kevin.brodsky@arm.com> writes:
> 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_HAS_LAZY_MMU_MODE 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_HAS_LAZY_MMU_MODE. 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(-)
Maybe we can add this to ... ?
Documentation/features/vm/lazy_mmu/arch-support.txt
#
# Feature name: lazy_mmu mode
# Kconfig: ARCH_HAS_LAZY_MMU_MODE
# description: arch supports arch_{enter|flush|leave}_lazy_mmu_mode()
#
-----------------------
| arch |status|
-----------------------
| arm64: | ok |
| powerpc: | ok |
| sparc: | ok |
| x86: | ok |
-----------------------
As for this patch, the changes are mostly straight forward around the
configs part. This looks good to me. Please feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
-ritesh
On 05/11/2025 04:40, Ritesh Harjani (IBM) wrote:
> Kevin Brodsky <kevin.brodsky@arm.com> writes:
>
>> 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_HAS_LAZY_MMU_MODE 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_HAS_LAZY_MMU_MODE. 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(-)
> Maybe we can add this to ... ?
>
> Documentation/features/vm/lazy_mmu/arch-support.txt
>
> #
> # Feature name: lazy_mmu mode
> # Kconfig: ARCH_HAS_LAZY_MMU_MODE
> # description: arch supports arch_{enter|flush|leave}_lazy_mmu_mode()
> #
> -----------------------
> | arch |status|
> -----------------------
> | arm64: | ok |
> | powerpc: | ok |
> | sparc: | ok |
> | x86: | ok |
> -----------------------
That's an interesting idea but I'm not sure it really makes sense for
lazy MMU? AFAIU these arch-support.txt files are meant to help identify
which generic features an arch has support for. Lazy MMU isn't really a
feature though, in the sense that what it does is entirely defined by
the arch. This patch does introduce a generic layer, but ultimately it
remains a collection of arch hooks.
> As for this patch, the changes are mostly straight forward around the
> configs part. This looks good to me. Please feel free to add:
>
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Thanks for the review!
- Kevin
On 29.10.25 11:09, 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_HAS_LAZY_MMU_MODE 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_HAS_LAZY_MMU_MODE. 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> > --- Acked-by: David Hildenbrand <david@redhat.com> -- Cheers David / dhildenb
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