linux-kernel - Re: [v2 PATCH] arm64: mm: make linear mapping permission update more robust for patial range

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Message-ID: <a6d3d2d3-32b5-4784-98d9-1b42a0ef4616@os.amperecomputing.com>
Date: Mon, 10 Nov 2025 15:08:37 -0800
From: Yang Shi <yang@...amperecomputing.com>
To: ryan.roberts@....com, dev.jain@....com, cl@...two.org,
 catalin.marinas@....com, will@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [v2 PATCH] arm64: mm: make linear mapping permission update more
 robust for patial range

Hi folks,

Gently ping...

It is not an urgent fix, either 6.18 or 6.19 is fine.

Thanks,
Yang


On 10/23/25 1:44 PM, Yang Shi wrote:
> The commit fcf8dda8cc48 ("arm64: pageattr: Explicitly bail out when changing
> permissions for vmalloc_huge mappings") made permission update for
> partial range more robust. But the linear mapping permission update
> still assumes update the whole range by iterating from the first page
> all the way to the last page of the area.
>
> Make it more robust by updating the linear mapping permission from the
> page mapped by start address, and update the number of numpages.
>
> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> Reviewed-by: Dev Jain <dev.jain@....com>
> Signed-off-by: Yang Shi <yang@...amperecomputing.com>
> ---
> v2: * Dropped the fixes tag per Ryan and Dev
>      * Simplified the loop per Dev
>      * Collected R-bs
>
>   arch/arm64/mm/pageattr.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 5135f2d66958..08ac96b9f846 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -148,7 +148,6 @@ static int change_memory_common(unsigned long addr, int numpages,
>   	unsigned long size = PAGE_SIZE * numpages;
>   	unsigned long end = start + size;
>   	struct vm_struct *area;
> -	int i;
>   
>   	if (!PAGE_ALIGNED(addr)) {
>   		start &= PAGE_MASK;
> @@ -184,8 +183,9 @@ static int change_memory_common(unsigned long addr, int numpages,
>   	 */
>   	if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
>   			    pgprot_val(clear_mask) == PTE_RDONLY)) {
> -		for (i = 0; i < area->nr_pages; i++) {
> -			__change_memory_common((u64)page_address(area->pages[i]),
> +		unsigned long idx = (start - (unsigned long)area->addr) >> PAGE_SHIFT;
> +		for (; numpages; idx++, numpages--) {
> +			__change_memory_common((u64)page_address(area->pages[idx]),
>   					       PAGE_SIZE, set_mask, clear_mask);
>   		}
>   	}