linux-kernel - Re: [PATCH v8 3/5] arm64: mm: support large block mapping when rodata=full

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Message-ID: <CABXOdTeOU0qeSicdDU6DjNHWpzCEhK-66kTdwWjb3M+=Xr3aMQ@mail.gmail.com>
Date: Sun, 2 Nov 2025 09:49:50 -0800
From: Guenter Roeck <groeck@...gle.com>
To: Ryan Roberts <linux@...ck-us.net>
Cc: Yang Shi <yang@...amperecomputing.com>, catalin.marinas@....com, will@...nel.org, 
	akpm@...ux-foundation.org, david@...hat.com, lorenzo.stoakes@...cle.com, 
	ardb@...nel.org, dev.jain@....com, scott@...amperecomputing.com, 
	cl@...two.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, nd@....com
Subject: Re: [PATCH v8 3/5] arm64: mm: support large block mapping when rodata=full

On Sun, Nov 2, 2025 at 7:09 AM Ryan Roberts <linux@...ck-us.net> wrote:
...
> commit 602ec2db74e5abfb058bd03934475ead8558eb72
> Author: Ryan Roberts <ryan.roberts@....com>
> Date:   Sun Nov 2 11:45:18 2025 +0000
>
>     arm64: mm: Don't attempt to split known pte-mapped regions
>
>     It has been reported that split_kernel_leaf_mapping() is trying to sleep
>     in non-sleepable context. It does this when acquiring the
>     pgtable_split_lock mutex, when either CONFIG_DEBUG_ALLOC or
>     CONFIG_KFENCE are enabled, which change linear map permissions within
>     softirq context during memory allocation and/or freeing.
>
>     But it turns out that the memory for which these features may attempt to
>     modify the permissions is always mapped by pte, so there is no need to
>     attempt to split the mapping. So let's exit early in these cases and
>     avoid attempting to take the mutex.
>
>     Closes: https://lore.kernel.org/all/f24b9032-0ec9-47b1-8b95-c0eeac7a31c5@roeck-us.net/
>     Fixes: a166563e7ec3 ("arm64: mm: support large block mapping when rodata=full")
>     Signed-off-by: Ryan Roberts <ryan.roberts@....com>

Tested-by: Guenter Roeck <groeck@...gle.com>

Thanks a lot for the quick turnaround!

Guenter