linux-kernel - Re: [PATCH v2 12/13] arm64: mm: Wrap flush_tlb_page() around ___flush_tlb

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Message-ID: <20260127125933.00006101@huawei.com>
Date: Tue, 27 Jan 2026 12:59:33 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ryan Roberts <ryan.roberts@....com>
CC: Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, Catalin
 Marinas <catalin.marinas@....com>, Mark Rutland <mark.rutland@....com>, Linus
 Torvalds <torvalds@...ux-foundation.org>, Oliver Upton
	<oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>, "Dev Jain"
	<dev.jain@....com>, Linu Cherian <Linu.Cherian@....com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 12/13] arm64: mm: Wrap flush_tlb_page() around
 ___flush_tlb_range()

On Mon, 19 Jan 2026 17:21:59 +0000
Ryan Roberts <ryan.roberts@....com> wrote:

> Flushing a page from the tlb is just a special case of flushing a range.
> So let's rework flush_tlb_page() so that it simply wraps
> ___flush_tlb_range(). While at it, let's also update the API to take the
> same flags that we use when flushing a range. This allows us to delete
> all the ugly "_nosync", "_local" and "_nonotify" variants.
> 
> Thanks to constant folding, all of the complex looping and tlbi-by-range
> options get eliminated so that the generated code for flush_tlb_page()
> looks very similar to the previous version.
> 
> Reviewed-by: Linu Cherian <linu.cherian@....com>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>

So this does include the use of the

Case TLBF_NOBROADCAST from previous patch, but only whilst (I think)
slightly changing behavior.

Gah.  I'm regretting looking at this series. The original code is really hard to
read :)  Rather you than me to fix it!

>  static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end)
>  {
>  	const unsigned long stride = PAGE_SIZE;
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index be9dab2c7d6a..f91aa686f142 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -239,7 +239,7 @@ int __ptep_set_access_flags(struct vm_area_struct *vma,
>  	 * flush_tlb_fix_spurious_fault().
>  	 */
>  	if (dirty)
> -		local_flush_tlb_page(vma, address);
> +		__flush_tlb_page(vma, address, TLBF_NOBROADCAST);

Ultimately I think this previously did __tlbi(vale1) and now does __tlbi(vae1)
Original call was to __local_flush_tlb_page_notify_nosync()

I'd like to see that sort of change called out and explained in the patch description.
It's a broader scoped flush so not a bug, but still a functional change.

>  	return 1;
>  }
>