Re: [PATCH v8 03/10] mm/vmalloc: use pte_set_huge()/pte_clear_huge() for PTE-level block mappings

["Christophe Leroy (CS GROUP)" <chleroy@kernel.org>]

Le 17/09/2026 à 07:29, Wen Jiang a écrit :
> From: Wen Jiang <jiangwen6@xiaomi.com>
> 
> vmap installs PTE-level block mappings by reusing set_huge_pte_at() and
> huge_ptep_get_and_clear() under #ifdef CONFIG_HUGETLB_PAGE. This makes
> the feature silently unavailable on CONFIG_HUGETLB_PAGE=n kernels and
> couples mm/vmalloc.c to HugeTLB internals it does not otherwise need.
> 
> Now that arm64 and powerpc/8xx provide pte_set_huge() and
> pte_clear_huge(), add the generic fallbacks next to the existing
> pmd/pud_set_huge() family and convert vmap_pte_range() and
> vunmap_pte_range() to the new helpers. The CONFIG_HUGETLB_PAGE guards
> around the block-mapping paths are dropped, so PTE-level block mappings
> now also work on CONFIG_HUGETLB_PAGE=n kernels, and mm/vmalloc.c no
> longer includes <linux/hugetlb.h>.
> 
> The fallbacks exist only to keep the build working on architectures
> without PTE-level block mapping support. They are unreachable there:
> the callers only run when arch_vmap_pte_range_map_size() or
> arch_vmap_pte_range_unmap_size() return a size other than PAGE_SIZE,
> which requires an arch implementation. WARN_ON_ONCE() makes that
> explicit rather than silently doing nothing.
> 
> Signed-off-by: Wen Jiang <jiangwen6@xiaomi.com>
> ---
>   include/linux/pgtable.h | 29 +++++++++++++++++++++++++++++
>   mm/vmalloc.c            | 19 ++++++-------------
>   2 files changed, 35 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index cdd68ed3ae1a9..349ced999f959 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -2134,6 +2134,35 @@ static inline int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>   }
>   #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
>   
> +/*
> + * PTE-level block mappings for vmap.
> + *
> + * pte_set_huge() only has to be implemented by architectures whose
> + * arch_vmap_pte_range_map_size() can return a size other than PAGE_SIZE.
> + */
> +#ifndef __HAVE_ARCH_PTE_SET_HUGE
> +static inline void pte_set_huge(pte_t *ptep, unsigned long addr,
> +				phys_addr_t phys, pgprot_t prot,
> +				unsigned long size)
> +{
> +	WARN_ON_ONCE(1);

BUILD_BUG_ON() would be better here.

It should be possible because fallback arch_vmap_pte_range_map_size() 
will constant-fold PAGE_SIZE so pte_set_huge() will never be called.

> +}
> +#endif
> +
> +/*
> + * Likewise, pte_clear_huge() only has to be implemented by architectures
> + * whose arch_vmap_pte_range_unmap_size() can return a size other than
> + * PAGE_SIZE.
> + */
> +#ifndef __HAVE_ARCH_PTE_CLEAR_HUGE
> +static inline pte_t pte_clear_huge(pte_t *ptep, unsigned long addr,
> +				   unsigned long size)
> +{
> +	WARN_ON_ONCE(1);
> +	return __pte(0);

Same I guess.

> +}
> +#endif
> +
>   #ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>   /*