Re: [PATCH v2 2/7] mm: introduce local state for lazy_mmu sections

Yeoreum Yun
2025-09-08T09:30:58Z

Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>

On Mon, Sep 08, 2025 at 08:39:26AM +0100, Kevin Brodsky wrote:
> arch_{enter,leave}_lazy_mmu_mode() currently have a stateless API
> (taking and returning no value). This is proving problematic in
> situations where leave() needs to restore some context back to its
> original state (before enter() was called). In particular, this
> makes it difficult to support the nesting of lazy_mmu sections -
> leave() does not know whether the matching enter() call occurred
> while lazy_mmu was already enabled, and whether to disable it or
> not.
>
> This patch gives all architectures the chance to store local state
> while inside a lazy_mmu section by making enter() return some value,
> storing it in a local variable, and having leave() take that value.
> That value is typed lazy_mmu_state_t - each architecture defining
> __HAVE_ARCH_ENTER_LAZY_MMU_MODE is free to define it as it sees fit.
> For now we define it as int everywhere, which is sufficient to
> support nesting.
>
> The diff is unfortunately rather large as all the API changes need
> to be done atomically. Main parts:
>
> * Changing the prototypes of arch_{enter,leave}_lazy_mmu_mode()
> in generic and arch code, and introducing lazy_mmu_state_t.
>
> * Introducing LAZY_MMU_{DEFAULT,NESTED} for future support of
> nesting. enter() always returns LAZY_MMU_DEFAULT for now.
> (linux/mm_types.h is not the most natural location for defining
> those constants, but there is no other obvious header that is
> accessible where arch's implement the helpers.)
>
> * Changing all lazy_mmu sections to introduce a lazy_mmu_state
> local variable, having enter() set it and leave() take it. Most of
> these changes were generated using the following Coccinelle script:
>
> @@
> @@
> {
> + lazy_mmu_state_t lazy_mmu_state;
> ...
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> ...
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> ...
> }
>
> * In a few cases (e.g. xen_flush_lazy_mmu()), a function knows that
> lazy_mmu is already enabled, and it temporarily disables it by
> calling leave() and then enter() again. Here we want to ensure
> that any operation between the leave() and enter() calls is
> completed immediately; for that reason we pass LAZY_MMU_DEFAULT to
> leave() to fully disable lazy_mmu. enter() will then re-enable it
> - this achieves the expected behaviour, whether nesting occurred
> before that function was called or not.
>
> Note: it is difficult to provide a default definition of
> lazy_mmu_state_t for architectures implementing lazy_mmu, because
> that definition would need to be available in
> arch/x86/include/asm/paravirt_types.h and adding a new generic
> #include there is very tricky due to the existing header soup.
>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> ---
> arch/arm64/include/asm/pgtable.h | 10 +++++++---
> .../include/asm/book3s/64/tlbflush-hash.h | 9 ++++++---
> arch/powerpc/mm/book3s64/hash_tlb.c | 10 ++++++----
> arch/powerpc/mm/book3s64/subpage_prot.c | 5 +++--
> arch/sparc/include/asm/tlbflush_64.h | 5 +++--
> arch/sparc/mm/tlb.c | 6 ++++--
> arch/x86/include/asm/paravirt.h | 6 ++++--
> arch/x86/include/asm/paravirt_types.h | 2 ++
> arch/x86/xen/enlighten_pv.c | 2 +-
> arch/x86/xen/mmu_pv.c | 2 +-
> fs/proc/task_mmu.c | 5 +++--
> include/linux/mm_types.h | 3 +++
> include/linux/pgtable.h | 6 ++++--
> mm/kasan/shadow.c | 4 ++--
> mm/madvise.c | 20 ++++++++++---------
> mm/memory.c | 20 +++++++++++--------
> mm/migrate_device.c | 5 +++--
> mm/mprotect.c | 5 +++--
> mm/mremap.c | 5 +++--
> mm/userfaultfd.c | 5 +++--
> mm/vmalloc.c | 15 ++++++++------
> mm/vmscan.c | 15 ++++++++------
> 22 files changed, 102 insertions(+), 63 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 728d7b6ed20a..816197d08165 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -81,7 +81,9 @@ static inline void queue_pte_barriers(void)
> }
>
> #define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
> -static inline void arch_enter_lazy_mmu_mode(void)
> +typedef int lazy_mmu_state_t;
> +
> +static inline lazy_mmu_state_t arch_enter_lazy_mmu_mode(void)
> {
> /*
> * lazy_mmu_mode is not supposed to permit nesting. But in practice this
> @@ -96,12 +98,14 @@ static inline void arch_enter_lazy_mmu_mode(void)
> */
>
> if (in_interrupt())
> - return;
> + return LAZY_MMU_DEFAULT;
>
> set_thread_flag(TIF_LAZY_MMU);
> +
> + return LAZY_MMU_DEFAULT;
> }
>
> -static inline void arch_leave_lazy_mmu_mode(void)
> +static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)
> {
> if (in_interrupt())
> return;
> diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> index 176d7fd79eeb..c9f1e819e567 100644
> --- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> @@ -25,13 +25,14 @@ 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
> +typedef int lazy_mmu_state_t;
>
> -static inline void arch_enter_lazy_mmu_mode(void)
> +static inline lazy_mmu_state_t arch_enter_lazy_mmu_mode(void)
> {
> struct ppc64_tlb_batch *batch;
>
> if (radix_enabled())
> - return;
> + return LAZY_MMU_DEFAULT;
> /*
> * apply_to_page_range can call us this preempt enabled when
> * operating on kernel page tables.
> @@ -39,9 +40,11 @@ static inline void arch_enter_lazy_mmu_mode(void)
> preempt_disable();
> batch = this_cpu_ptr(&ppc64_tlb_batch);
> batch->active = 1;
> +
> + return LAZY_MMU_DEFAULT;
> }
>
> -static inline void arch_leave_lazy_mmu_mode(void)
> +static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)
> {
> struct ppc64_tlb_batch *batch;
>
> diff --git a/arch/powerpc/mm/book3s64/hash_tlb.c b/arch/powerpc/mm/book3s64/hash_tlb.c
> index 21fcad97ae80..ee664f88e679 100644
> --- a/arch/powerpc/mm/book3s64/hash_tlb.c
> +++ b/arch/powerpc/mm/book3s64/hash_tlb.c
> @@ -189,6 +189,7 @@ void hash__tlb_flush(struct mmu_gather *tlb)
> */
> void __flush_hash_table_range(unsigned long start, unsigned long end)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int hugepage_shift;
> unsigned long flags;
>
> @@ -205,7 +206,7 @@ void __flush_hash_table_range(unsigned long start, unsigned long end)
> * way to do things but is fine for our needs here.
> */
> local_irq_save(flags);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> for (; start < end; start += PAGE_SIZE) {
> pte_t *ptep = find_init_mm_pte(start, &hugepage_shift);
> unsigned long pte;
> @@ -217,12 +218,13 @@ void __flush_hash_table_range(unsigned long start, unsigned long end)
> continue;
> hpte_need_flush(&init_mm, start, ptep, pte, hugepage_shift);
> }
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> local_irq_restore(flags);
> }
>
> void flush_hash_table_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte;
> pte_t *start_pte;
> unsigned long flags;
> @@ -237,7 +239,7 @@ void flush_hash_table_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long
> * way to do things but is fine for our needs here.
> */
> local_irq_save(flags);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> start_pte = pte_offset_map(pmd, addr);
> if (!start_pte)
> goto out;
> @@ -249,6 +251,6 @@ void flush_hash_table_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long
> }
> pte_unmap(start_pte);
> out:
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> local_irq_restore(flags);
> }
> diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c b/arch/powerpc/mm/book3s64/subpage_prot.c
> index ec98e526167e..4720f9f321af 100644
> --- a/arch/powerpc/mm/book3s64/subpage_prot.c
> +++ b/arch/powerpc/mm/book3s64/subpage_prot.c
> @@ -53,6 +53,7 @@ void subpage_prot_free(struct mm_struct *mm)
> static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
> int npages)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pgd_t *pgd;
> p4d_t *p4d;
> pud_t *pud;
> @@ -73,13 +74,13 @@ static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
> pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> if (!pte)
> return;
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> for (; npages > 0; --npages) {
> pte_update(mm, addr, pte, 0, 0, 0);
> addr += PAGE_SIZE;
> ++pte;
> }
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(pte - 1, ptl);
> }
>
> diff --git a/arch/sparc/include/asm/tlbflush_64.h b/arch/sparc/include/asm/tlbflush_64.h
> index cd144eb31bdd..02c93a4e6af5 100644
> --- a/arch/sparc/include/asm/tlbflush_64.h
> +++ b/arch/sparc/include/asm/tlbflush_64.h
> @@ -40,10 +40,11 @@ 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
> +typedef int lazy_mmu_state_t;
>
> void flush_tlb_pending(void);
> -void arch_enter_lazy_mmu_mode(void);
> -void arch_leave_lazy_mmu_mode(void);
> +lazy_mmu_state_t arch_enter_lazy_mmu_mode(void);
> +void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state);
>
> /* Local cpu only. */
> void __flush_tlb_all(void);
> diff --git a/arch/sparc/mm/tlb.c b/arch/sparc/mm/tlb.c
> index a35ddcca5e76..bf5094b770af 100644
> --- a/arch/sparc/mm/tlb.c
> +++ b/arch/sparc/mm/tlb.c
> @@ -50,16 +50,18 @@ void flush_tlb_pending(void)
> put_cpu_var(tlb_batch);
> }
>
> -void arch_enter_lazy_mmu_mode(void)
> +lazy_mmu_state_t arch_enter_lazy_mmu_mode(void)
> {
> struct tlb_batch *tb;
>
> preempt_disable();
> tb = this_cpu_ptr(&tlb_batch);
> tb->active = 1;
> +
> + return LAZY_MMU_DEFAULT;
> }
>
> -void arch_leave_lazy_mmu_mode(void)
> +void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)
> {
> struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
>
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index b5e59a7ba0d0..65a0d394fba1 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -527,12 +527,14 @@ static inline void arch_end_context_switch(struct task_struct *next)
> }
>
> #define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
> -static inline void arch_enter_lazy_mmu_mode(void)
> +static inline lazy_mmu_state_t arch_enter_lazy_mmu_mode(void)
> {
> PVOP_VCALL0(mmu.lazy_mode.enter);
> +
> + return LAZY_MMU_DEFAULT;
> }
>
> -static inline void arch_leave_lazy_mmu_mode(void)
> +static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)
> {
> PVOP_VCALL0(mmu.lazy_mode.leave);
> }
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index 37a8627d8277..bc1af86868a3 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -41,6 +41,8 @@ struct pv_info {
> };
>
> #ifdef CONFIG_PARAVIRT_XXL
> +typedef int lazy_mmu_state_t;
> +
> struct pv_lazy_ops {
> /* Set deferred update mode, used for batching operations. */
> void (*enter)(void);
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index 26bbaf4b7330..a245ba47a631 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -426,7 +426,7 @@ static void xen_start_context_switch(struct task_struct *prev)
> BUG_ON(preemptible());
>
> if (this_cpu_read(xen_lazy_mode) == XEN_LAZY_MMU) {
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(LAZY_MMU_DEFAULT);
> set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
> }
> enter_lazy(XEN_LAZY_CPU);
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 2a4a8deaf612..2039d5132ca3 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -2140,7 +2140,7 @@ static void xen_flush_lazy_mmu(void)
> preempt_disable();
>
> if (xen_get_lazy_mode() == XEN_LAZY_MMU) {
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(LAZY_MMU_DEFAULT);
> arch_enter_lazy_mmu_mode();
> }
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ced01cf3c5ab..02aa55f83bae 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -2682,6 +2682,7 @@ static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
> static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
> unsigned long end, struct mm_walk *walk)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> struct pagemap_scan_private *p = walk->private;
> struct vm_area_struct *vma = walk->vma;
> unsigned long addr, flush_end = 0;
> @@ -2700,7 +2701,7 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
> return 0;
> }
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> if ((p->arg.flags & PM_SCAN_WP_MATCHING) && !p->vec_out) {
> /* Fast path for performing exclusive WP */
> @@ -2770,7 +2771,7 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
> if (flush_end)
> flush_tlb_range(vma, start, addr);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
>
> cond_resched();
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 275e8060d918..143d819c1386 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -1489,6 +1489,9 @@ extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
> extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
> extern void tlb_finish_mmu(struct mmu_gather *tlb);
>
> +#define LAZY_MMU_DEFAULT 0
> +#define LAZY_MMU_NESTED 1
> +
> struct vm_fault;
>
> /**
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 8d6007123cdf..df0eb898b3fc 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -232,8 +232,10 @@ static inline int pmd_dirty(pmd_t pmd)
> * and the mode cannot be used in interrupt context.
> */
> #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
> -#define arch_enter_lazy_mmu_mode() do {} while (0)
> -#define arch_leave_lazy_mmu_mode() do {} while (0)
> +typedef int lazy_mmu_state_t;
> +
> +#define arch_enter_lazy_mmu_mode() (LAZY_MMU_DEFAULT)
> +#define arch_leave_lazy_mmu_mode(state) ((void)(state))
> #endif
>
> #ifndef pte_batch_hint
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 5d2a876035d6..60b1b72f5ce1 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -305,7 +305,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
> pte_t pte;
> int index;
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(LAZY_MMU_DEFAULT);
>
> index = PFN_DOWN(addr - data->start);
> page = data->pages[index];
> @@ -482,7 +482,7 @@ static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
> pte_t pte;
> int none;
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(LAZY_MMU_DEFAULT);
>
> spin_lock(&init_mm.page_table_lock);
> pte = ptep_get(ptep);
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 35ed4ab0d7c5..72c032f2cf56 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -357,6 +357,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> unsigned long addr, unsigned long end,
> struct mm_walk *walk)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> struct madvise_walk_private *private = walk->private;
> struct mmu_gather *tlb = private->tlb;
> bool pageout = private->pageout;
> @@ -455,7 +456,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> if (!start_pte)
> return 0;
> flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> for (; addr < end; pte += nr, addr += nr * PAGE_SIZE) {
> nr = 1;
> ptent = ptep_get(pte);
> @@ -463,7 +464,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> if (++batch_count == SWAP_CLUSTER_MAX) {
> batch_count = 0;
> if (need_resched()) {
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
> cond_resched();
> goto restart;
> @@ -499,7 +500,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> if (!folio_trylock(folio))
> continue;
> folio_get(folio);
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
> start_pte = NULL;
> err = split_folio(folio);
> @@ -510,7 +511,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> if (!start_pte)
> break;
> flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> if (!err)
> nr = 0;
> continue;
> @@ -558,7 +559,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> }
>
> if (start_pte) {
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
> }
> if (pageout)
> @@ -657,6 +658,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>
> {
> const cydp_t cydp_flags = CYDP_CLEAR_YOUNG | CYDP_CLEAR_DIRTY;
> + lazy_mmu_state_t lazy_mmu_state;
> struct mmu_gather *tlb = walk->private;
> struct mm_struct *mm = tlb->mm;
> struct vm_area_struct *vma = walk->vma;
> @@ -677,7 +679,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> if (!start_pte)
> return 0;
> flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> for (; addr != end; pte += nr, addr += PAGE_SIZE * nr) {
> nr = 1;
> ptent = ptep_get(pte);
> @@ -727,7 +729,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> if (!folio_trylock(folio))
> continue;
> folio_get(folio);
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
> start_pte = NULL;
> err = split_folio(folio);
> @@ -738,7 +740,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> if (!start_pte)
> break;
> flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> if (!err)
> nr = 0;
> continue;
> @@ -778,7 +780,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> if (nr_swap)
> add_mm_counter(mm, MM_SWAPENTS, nr_swap);
> if (start_pte) {
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(start_pte, ptl);
> }
> cond_resched();
> diff --git a/mm/memory.c b/mm/memory.c
> index d9de6c056179..a60aae069f1e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1207,6 +1207,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
> pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
> unsigned long end)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> struct mm_struct *dst_mm = dst_vma->vm_mm;
> struct mm_struct *src_mm = src_vma->vm_mm;
> pte_t *orig_src_pte, *orig_dst_pte;
> @@ -1254,7 +1255,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
> spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
> orig_src_pte = src_pte;
> orig_dst_pte = dst_pte;
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> do {
> nr = 1;
> @@ -1323,7 +1324,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
> } while (dst_pte += nr, src_pte += nr, addr += PAGE_SIZE * nr,
> addr != end);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(orig_src_pte, src_ptl);
> add_mm_rss_vec(dst_mm, rss);
> pte_unmap_unlock(orig_dst_pte, dst_ptl);
> @@ -1822,6 +1823,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> unsigned long addr, unsigned long end,
> struct zap_details *details)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> bool force_flush = false, force_break = false;
> struct mm_struct *mm = tlb->mm;
> int rss[NR_MM_COUNTERS];
> @@ -1842,7 +1844,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> return addr;
>
> flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> do {
> bool any_skipped = false;
>
> @@ -1874,7 +1876,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> direct_reclaim = try_get_and_clear_pmd(mm, pmd, &pmdval);
>
> add_mm_rss_vec(mm, rss);
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
>
> /* Do the actual TLB flush before dropping ptl */
> if (force_flush) {
> @@ -2811,6 +2813,7 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
> unsigned long addr, unsigned long end,
> unsigned long pfn, pgprot_t prot)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte, *mapped_pte;
> spinlock_t *ptl;
> int err = 0;
> @@ -2818,7 +2821,7 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
> mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
> if (!pte)
> return -ENOMEM;
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> do {
> BUG_ON(!pte_none(ptep_get(pte)));
> if (!pfn_modify_allowed(pfn, prot)) {
> @@ -2828,7 +2831,7 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
> set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
> pfn++;
> } while (pte++, addr += PAGE_SIZE, addr != end);
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(mapped_pte, ptl);
> return err;
> }
> @@ -3117,6 +3120,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
> pte_fn_t fn, void *data, bool create,
> pgtbl_mod_mask *mask)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte, *mapped_pte;
> int err = 0;
> spinlock_t *ptl;
> @@ -3135,7 +3139,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
> return -EINVAL;
> }
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> if (fn) {
> do {
> @@ -3148,7 +3152,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
> }
> *mask |= PGTBL_PTE_MODIFIED;
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
>
> if (mm != &init_mm)
> pte_unmap_unlock(mapped_pte, ptl);
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index abd9f6850db6..833ce5eafa40 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -59,6 +59,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> unsigned long end,
> struct mm_walk *walk)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> struct migrate_vma *migrate = walk->private;
> struct folio *fault_folio = migrate->fault_page ?
> page_folio(migrate->fault_page) : NULL;
> @@ -110,7 +111,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
> if (!ptep)
> goto again;
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> for (; addr < end; addr += PAGE_SIZE, ptep++) {
> struct dev_pagemap *pgmap;
> @@ -287,7 +288,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> if (unmapped)
> flush_tlb_range(walk->vma, start, end);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(ptep - 1, ptl);
>
> return 0;
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 113b48985834..7bba651e5aa3 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -273,6 +273,7 @@ static long change_pte_range(struct mmu_gather *tlb,
> struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr,
> unsigned long end, pgprot_t newprot, unsigned long cp_flags)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte, oldpte;
> spinlock_t *ptl;
> long pages = 0;
> @@ -293,7 +294,7 @@ static long change_pte_range(struct mmu_gather *tlb,
> target_node = numa_node_id();
>
> flush_tlb_batched_pending(vma->vm_mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> do {
> nr_ptes = 1;
> oldpte = ptep_get(pte);
> @@ -439,7 +440,7 @@ static long change_pte_range(struct mmu_gather *tlb,
> }
> }
> } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end);
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(pte - 1, ptl);
>
> return pages;
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 35de0a7b910e..a562d8cf1eee 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -193,6 +193,7 @@ static int mremap_folio_pte_batch(struct vm_area_struct *vma, unsigned long addr
> static int move_ptes(struct pagetable_move_control *pmc,
> unsigned long extent, pmd_t *old_pmd, pmd_t *new_pmd)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> struct vm_area_struct *vma = pmc->old;
> bool need_clear_uffd_wp = vma_has_uffd_without_event_remap(vma);
> struct mm_struct *mm = vma->vm_mm;
> @@ -256,7 +257,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
> if (new_ptl != old_ptl)
> spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
> flush_tlb_batched_pending(vma->vm_mm);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> for (; old_addr < old_end; old_ptep += nr_ptes, old_addr += nr_ptes * PAGE_SIZE,
> new_ptep += nr_ptes, new_addr += nr_ptes * PAGE_SIZE) {
> @@ -301,7 +302,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
> }
> }
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> if (force_flush)
> flush_tlb_range(vma, old_end - len, old_end);
> if (new_ptl != old_ptl)
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index 50aaa8dcd24c..6ee71ba68b12 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -1076,6 +1076,7 @@ static long move_present_ptes(struct mm_struct *mm,
> struct folio **first_src_folio, unsigned long len,
> struct anon_vma *src_anon_vma)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int err = 0;
> struct folio *src_folio = *first_src_folio;
> unsigned long src_start = src_addr;
> @@ -1100,7 +1101,7 @@ static long move_present_ptes(struct mm_struct *mm,
> /* It's safe to drop the reference now as the page-table is holding one. */
> folio_put(*first_src_folio);
> *first_src_folio = NULL;
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> while (true) {
> orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte);
> @@ -1138,7 +1139,7 @@ static long move_present_ptes(struct mm_struct *mm,
> break;
> }
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> if (src_addr > src_start)
> flush_tlb_range(src_vma, src_start, src_addr);
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4249e1e01947..9fc86ddf1711 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -95,6 +95,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> phys_addr_t phys_addr, pgprot_t prot,
> unsigned int max_page_shift, pgtbl_mod_mask *mask)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte;
> u64 pfn;
> struct page *page;
> @@ -105,7 +106,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> if (!pte)
> return -ENOMEM;
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> do {
> if (unlikely(!pte_none(ptep_get(pte)))) {
> @@ -131,7 +132,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> pfn++;
> } while (pte += PFN_DOWN(size), addr += size, addr != end);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> *mask |= PGTBL_PTE_MODIFIED;
> return 0;
> }
> @@ -354,12 +355,13 @@ int ioremap_page_range(unsigned long addr, unsigned long end,
> static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> pgtbl_mod_mask *mask)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> pte_t *pte;
> pte_t ptent;
> unsigned long size = PAGE_SIZE;
>
> pte = pte_offset_kernel(pmd, addr);
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> do {
> #ifdef CONFIG_HUGETLB_PAGE
> @@ -378,7 +380,7 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> WARN_ON(!pte_none(ptent) && !pte_present(ptent));
> } while (pte += (size >> PAGE_SHIFT), addr += size, addr != end);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> *mask |= PGTBL_PTE_MODIFIED;
> }
>
> @@ -514,6 +516,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
> unsigned long end, pgprot_t prot, struct page **pages, int *nr,
> pgtbl_mod_mask *mask)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int err = 0;
> pte_t *pte;
>
> @@ -526,7 +529,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
> if (!pte)
> return -ENOMEM;
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> do {
> struct page *page = pages[*nr];
> @@ -548,7 +551,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
> (*nr)++;
> } while (pte++, addr += PAGE_SIZE, addr != end);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> *mask |= PGTBL_PTE_MODIFIED;
>
> return err;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index ca9e1cd3cd68..2872497a0453 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3514,6 +3514,7 @@ static void walk_update_folio(struct lru_gen_mm_walk *walk, struct folio *folio,
> static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> struct mm_walk *args)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int i;
> bool dirty;
> pte_t *pte;
> @@ -3543,7 +3544,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> return false;
> }
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
> restart:
> for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
> unsigned long pfn;
> @@ -3584,7 +3585,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
> goto restart;
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> pte_unmap_unlock(pte, ptl);
>
> return suitable_to_scan(total, young);
> @@ -3593,6 +3594,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
> struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int i;
> bool dirty;
> pmd_t *pmd;
> @@ -3625,7 +3627,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
> if (!spin_trylock(ptl))
> goto done;
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> do {
> unsigned long pfn;
> @@ -3672,7 +3674,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
>
> walk_update_folio(walk, last, gen, dirty);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
> spin_unlock(ptl);
> done:
> *first = -1;
> @@ -4220,6 +4222,7 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
> */
> bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
> {
> + lazy_mmu_state_t lazy_mmu_state;
> int i;
> bool dirty;
> unsigned long start;
> @@ -4271,7 +4274,7 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
> }
> }
>
> - arch_enter_lazy_mmu_mode();
> + lazy_mmu_state = arch_enter_lazy_mmu_mode();
>
> pte -= (addr - start) / PAGE_SIZE;
>
> @@ -4305,7 +4308,7 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
>
> walk_update_folio(walk, last, gen, dirty);
>
> - arch_leave_lazy_mmu_mode();
> + arch_leave_lazy_mmu_mode(lazy_mmu_state);
>
> /* feedback from rmap walkers to page table walkers */
> if (mm_state && suitable_to_scan(i, young))
> --
> 2.47.0
>

--
Sincerely,
Yeoreum Yun