Re: [PATCH v9 05/10] arm64/vmalloc: allow arch_vmap_pte_range_map_size() to batch multiple CONT_PTE

[Uladzislau Rezki <urezki@gmail.com>]

On Wed, Sep 23, 2026 at 02:28:27PM +0800, Wen Jiang wrote:
> From: "Barry Song (Xiaomi)" <baohua@kernel.org>
> 
> Allow arch_vmap_pte_range_map_size to batch across multiple CONT_PTE
> blocks, reducing both PTE setup and TLB flush iterations.
> 
> For CONT_PTE_SIZE-aligned ranges, return a mapping size that may cover
> multiple CONT_PTE blocks, capped below PMD_SIZE. These sizes are vmalloc
> mapping spans, not HugeTLB hstate sizes.
> 
> Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
> Signed-off-by: Wen Jiang <jiangwen6@xiaomi.com>
> Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
> Tested-by: Leo Yan <leo.yan@arm.com>
> ---
>  arch/arm64/include/asm/vmalloc.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
> index 4ec1acd3c1b34..4053b1ec1902e 100644
> --- a/arch/arm64/include/asm/vmalloc.h
> +++ b/arch/arm64/include/asm/vmalloc.h
> @@ -23,10 +23,14 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr,
>  						unsigned long end, u64 pfn,
>  						unsigned int max_page_shift)
>  {
> +	unsigned long size;
> +
>  	/*
>  	 * If the block is at least CONT_PTE_SIZE in size, and is naturally
>  	 * aligned in both virtual and physical space, then we can pte-map the
>  	 * block using the PTE_CONT bit for more efficient use of the TLB.
> +	 * The returned mapping size may cover multiple CONT_PTE_SIZE blocks,
> +	 * capped below PMD_SIZE.
>  	 */
>  	if (max_page_shift < CONT_PTE_SHIFT)
>  		return PAGE_SIZE;
> @@ -40,7 +44,9 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr,
>  	if (!IS_ALIGNED(PFN_PHYS(pfn), CONT_PTE_SIZE))
>  		return PAGE_SIZE;
>  
> -	return CONT_PTE_SIZE;
> +	size = min3(end - addr, 1UL << max_page_shift, PMD_SIZE >> 1);
>
Capped below PMD_SIZE? It is half of PMD_SIZE. Where is that limitation
comes from? I think the commit message should be improved in that sense.

--
Uladzislau Rezki