Re: [PATCH] sparc: Use vmemmap_populate_hugepages for vmemmap_populate

["David Hildenbrand (Red Hat)" <david@kernel.org>]

On 12/17/25 13:08, chengkaitao wrote:
> From: Chengkaitao <chengkaitao@kylinos.cn>
> 
> 1. Added the vmemmap_false_pmd function to accommodate architectures
> that do not support basepages.
> 2. In the SPARC architecture, reimplemented vmemmap_populate using
> vmemmap_populate_hugepages.
> 
> Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
> ---
>   arch/sparc/mm/init_64.c | 56 ++++++++++++++++-------------------------
>   include/linux/mm.h      |  1 +
>   mm/sparse-vmemmap.c     |  7 +++++-
>   3 files changed, 28 insertions(+), 36 deletions(-)
> 
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index df9f7c444c39..a80cdfa6ba98 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -5,7 +5,7 @@
>    *  Copyright (C) 1996-1999 David S. Miller (davem@caip.rutgers.edu)
>    *  Copyright (C) 1997-1999 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
>    */
> -
> +
>   #include <linux/extable.h>
>   #include <linux/kernel.h>
>   #include <linux/sched.h>
> @@ -2397,11 +2397,11 @@ void __init paging_init(void)
>   	 * work.
>   	 */
>   	init_mm.pgd += ((shift) / (sizeof(pgd_t)));
> -	
> +
>   	memset(swapper_pg_dir, 0, sizeof(swapper_pg_dir));
>   
>   	inherit_prom_mappings();
> -	
> +
>   	/* Ok, we can use our TLB miss and window trap handlers safely.  */
>   	setup_tba();
>   

Bunch of unrelated changes that should not go in here.

> @@ -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 +2595,25 @@ 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);
> +	pmd_val(*pmd) = pte_base | __pa(p);
> +}
>   
> -			if (!block)
> -				return -ENOMEM;
> +bool __meminit vmemmap_false_pmd(pmd_t *pmd, int node)
> +{
> +	return true;
> +}
>   
> -			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;
> +}
>   
> -	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 */
>   
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 15076261d0c2..5e005b0f947d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -4248,6 +4248,7 @@ void *vmemmap_alloc_block_buf(unsigned long size, int node,
>   void vmemmap_verify(pte_t *, int, unsigned long, unsigned long);
>   void vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
>   		     unsigned long addr, unsigned long next);
> +bool vmemmap_false_pmd(pmd_t *pmd, int node);
>   int vmemmap_check_pmd(pmd_t *pmd, int node,
>   		      unsigned long addr, unsigned long next);
>   int vmemmap_populate_basepages(unsigned long start, unsigned long end,
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 37522d6cb398..bd54b8c6f56e 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -407,6 +407,11 @@ void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
>   {
>   }
>   
> +bool __weak __meminit vmemmap_false_pmd(pmd_t *pmd, int node)
> +{
> +	return 0;
> +}
> +

Reading that function I have absolutely no clue what this is supposed to 
do. :)

Also, why are you passing pmd+node when sparc ignores them completely 
and statically returns "true" ?

If you can tell me what the semantics of that function should be, maybe 
we can come up with a more descriptive name.

-- 
Cheers

David