Re: [PATCH v3 1/3] sparc: Use vmemmap_populate_hugepages for vmemmap_populate

[Mike Rapoport <rppt@kernel.org>]

On Fri, Dec 19, 2025 at 01:47:47AM +0800, chengkaitao wrote:
> From: Chengkaitao <chengkaitao@kylinos.cn>
> 
> 1. In the SPARC architecture, reimplemented vmemmap_populate using
> vmemmap_populate_hugepages.
> 2. Allow the SPARC arch to fallback to vmemmap_populate_basepages(),
> when vmemmap_alloc_block returns NULL.
> 
> Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
> ---
>  arch/sparc/mm/init_64.c | 47 ++++++++++++-----------------------------
>  1 file changed, 14 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index df9f7c444c39..f477ab1b4f08 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -2581,8 +2581,8 @@ unsigned long _PAGE_CACHE __read_mostly;
>  EXPORT_SYMBOL(_PAGE_CACHE);
>  
>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
> -int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> -			       int node, struct vmem_altmap *altmap)
> +void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
> +			       unsigned long addr, unsigned long next)
>  {
>  	unsigned long pte_base;
>  
> @@ -2595,39 +2595,20 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
>  
>  	pte_base |= _PAGE_PMD_HUGE;
>  
> -	vstart = vstart & PMD_MASK;
> -	vend = ALIGN(vend, PMD_SIZE);
> -	for (; vstart < vend; vstart += PMD_SIZE) {
> -		pgd_t *pgd = vmemmap_pgd_populate(vstart, node);
> -		unsigned long pte;
> -		p4d_t *p4d;
> -		pud_t *pud;
> -		pmd_t *pmd;
> -
> -		if (!pgd)
> -			return -ENOMEM;
> -
> -		p4d = vmemmap_p4d_populate(pgd, vstart, node);
> -		if (!p4d)
> -			return -ENOMEM;
> -
> -		pud = vmemmap_pud_populate(p4d, vstart, node);
> -		if (!pud)
> -			return -ENOMEM;
> -
> -		pmd = pmd_offset(pud, vstart);
> -		pte = pmd_val(*pmd);
> -		if (!(pte & _PAGE_VALID)) {
> -			void *block = vmemmap_alloc_block(PMD_SIZE, node);
> -
> -			if (!block)
> -				return -ENOMEM;
> +	pmd_val(*pmd) = pte_base | __pa(p);
> +}
>  
> -			pmd_val(*pmd) = pte_base | __pa(block);
> -		}
> -	}
> +int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> +				unsigned long addr, unsigned long next)
> +{
> +	vmemmap_verify((pte_t *)pmdp, node, addr, next);
> +	return 1;

This should return 1 only if the pmd actually maps a large page, see x86
and powerpc implementations for example.

> +}
>  
> -	return 0;
> +int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> +			       int node, struct vmem_altmap *altmap)
> +{
> +	return vmemmap_populate_hugepages(vstart, vend, node, altmap);
>  }
>  #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>  
> -- 
> 2.50.1 (Apple Git-155)
> 

-- 
Sincerely yours,
Mike.