Re: [PATCH] sparc64: replace move_pte() with a D-cache flush in flush_cache_range()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Wed, Nov 04, 2026 at 11:52:58AM +0100, Imre Kaloz wrote:
> mremap() can move a page to an address of the other D-cache color,
> leaving lines of the old color in the virtually indexed D-cache of
> Spitfire and Cheetah CPUs.  move_pte() flushed the page for each PTE
> moved, which is only correct while move_ptes() handles one PTE at a
> time.
>
> Drop move_pte(), which no other architecture defines, and flush the
> whole D-cache in flush_cache_range(), which mremap() calls on the old
> range before moving the PTEs.  This keeps the fix in sparc64 without
> a page table walk.
>
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Link: https://lore.kernel.org/all/409079fe-ab52-4389-9fe0-d7246eb27bad@kernel.org/
> Signed-off-by: Imre Kaloz <kaloz@kernel.org>

Oh lovely thanks :) LGTM!

Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
> Andreas asked for this as a separate patch once the merge window was
> over [1]. It applies on top of sparc for-next.
>
> [1] https://lore.kernel.org/all/4fba060e-c4f4-4d73-8efe-dbed0b5a7bc3@gaisler.com/
>
>  arch/sparc/include/asm/cacheflush_64.h |  4 ++--
>  arch/sparc/include/asm/pgtable_64.h    | 21 ---------------------
>  arch/sparc/mm/init_64.c                | 18 ++++++++++++++++++
>  include/linux/pgtable.h                |  4 ----
>  mm/mremap.c                            |  1 -
>  5 files changed, 20 insertions(+), 28 deletions(-)
>
> diff --git a/arch/sparc/include/asm/cacheflush_64.h b/arch/sparc/include/asm/cacheflush_64.h
> index 54a2d37008e6..1a116b288816 100644
> --- a/arch/sparc/include/asm/cacheflush_64.h
> +++ b/arch/sparc/include/asm/cacheflush_64.h
> @@ -21,8 +21,8 @@ void __flushw_user(void);
>  #define flush_cache_mm(__mm) \
>  	do { if ((__mm) == current->mm) flushw_user(); } while(0)
>  #define flush_cache_dup_mm(mm) flush_cache_mm(mm)
> -#define flush_cache_range(vma, start, end) \
> -	flush_cache_mm((vma)->vm_mm)
> +void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
> +		       unsigned long end);
>  #define flush_cache_page(vma, page, pfn) \
>  	flush_cache_mm((vma)->vm_mm)
>
> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> index c26f2888aa18..310b66459521 100644
> --- a/arch/sparc/include/asm/pgtable_64.h
> +++ b/arch/sparc/include/asm/pgtable_64.h
> @@ -935,27 +935,6 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
>  #define pte_clear(mm,addr,ptep)		\
>  	set_pte_at((mm), (addr), (ptep), __pte(0UL))
>
> -#ifdef DCACHE_ALIASING_POSSIBLE
> -/* This flushes only the page the PTE maps, so it relies on move_ptes()
> - * calling it for one PTE at a time, which the default pte_batch_hint()
> - * guarantees.
> - */
> -#define __HAVE_ARCH_MOVE_PTE
> -#define move_pte(pte, old_addr, new_addr)				\
> -({									\
> -	pte_t newpte = (pte);						\
> -	if (tlb_type != hypervisor && pte_present(pte)) {		\
> -		unsigned long this_pfn = pte_pfn(pte);			\
> -									\
> -		if (pfn_valid(this_pfn) &&				\
> -		    (((old_addr) ^ (new_addr)) & (1 << 13)))		\
> -			flush_dcache_page_all(current->mm,		\
> -					      pfn_to_page(this_pfn));	\
> -	}								\
> -	newpte;								\
> -})
> -#endif
> -
>  extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
>
>  void paging_init(void);
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index 6a0ba9a01a21..a1ab1eacbf33 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -3115,6 +3115,24 @@ void flush_cache_vmap(unsigned long start, unsigned long end)
>  #endif
>  }
>
> +/*
> + * mremap() moves the PTEs of [start, end) to addresses that may have the
> + * other color, and calls this on the old range first.  Flush the whole
> + * D-cache so no line of the old color outlives the move.
> + */
> +void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
> +		       unsigned long end)
> +{
> +	/* flush_cache_mm() spills the user register windows. */
> +	flush_cache_mm(vma->vm_mm);
> +#ifdef DCACHE_ALIASING_POSSIBLE
> +	/* The D-cache is virtually indexed on Spitfire and Cheetah. */
> +	if (tlb_type == spitfire || tlb_type == cheetah ||
> +	    tlb_type == cheetah_plus)
> +		flush_dcache_all();
> +#endif
> +}
> +
>  void flush_tlb_kernel_range(unsigned long start, unsigned long end)
>  {
>  	if (start < HI_OBP_ADDRESS && end > LOW_OBP_ADDRESS) {
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 780fe849ff8b..c729c3cc8bda 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1470,10 +1470,6 @@ static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
>  }
>  #endif
>
> -#ifndef __HAVE_ARCH_MOVE_PTE
> -#define move_pte(pte, old_addr, new_addr)	(pte)
> -#endif
> -
>  #ifndef pte_accessible
>  # define pte_accessible(mm, pte)	((void)(pte), 1)
>  #endif
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 0d06d7f37f19..87cb15027bfd 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -289,7 +289,6 @@ static int move_ptes(struct pagetable_move_control *pmc,
>  			force_flush = true;
>  		}
>  		pte = get_and_clear_ptes(mm, old_addr, old_ptep, nr_ptes);
> -		pte = move_pte(pte, old_addr, new_addr);

:))

>  		pte = move_soft_dirty_pte(pte);
>
>  		if (need_clear_uffd_wp && pte_is_uffd_wp_marker(pte))
>
> base-commit: c95443b98771a74c6689f5e7bbc56794fe95f550
> --
> 2.47.3
>

--
Cheers, Lorenzo