[PATCH 1/4] arm64: tlb: Use __tlbi_sync_s1ish_kernel() for kernel TLB maintenance

[Mark Rutland]

Hi Catalin,

On Mon, Mar 02, 2026 at 04:57:54PM +0000, Catalin Marinas wrote:
> Add __tlbi_sync_s1ish_kernel() similar to __tlbi_sync_s1ish() and use it
> for kernel TLB maintenance. Also use this function in flush_tlb_all()
> which is only used in relation to kernel mappings. Subsequent patches
> can differentiate between workarounds that apply to user only or both
> user and kernel.
> 
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Mark Rutland <mark.rutland at arm.com>

This looks fine to me. I have one minor comment/naming nit below, but
this looks functionally correct, and I'm happy to spin a follow-up for
that.

With or without the changes below:

Acked-by: Mark Rutland <mark.rutland at arm.com>

> ---
>  arch/arm64/include/asm/tlbflush.h | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index 1416e652612b..19be0f7bfca5 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -191,6 +191,12 @@ static inline void __tlbi_sync_s1ish(void)
>  	__repeat_tlbi_sync(vale1is, 0);
>  }
>  
> +static inline void __tlbi_sync_s1ish_kernel(void)
> +{
> +	dsb(ish);
> +	__repeat_tlbi_sync(vale1is, 0);
> +}
> +
>  /*
>   * Complete broadcast TLB maintenance issued by hyp code which invalidates
>   * stage 1 translation information in any translation regime.
> @@ -299,7 +305,7 @@ static inline void flush_tlb_all(void)
>  {
>  	dsb(ishst);
>  	__tlbi(vmalle1is);
> -	__tlbi_sync_s1ish();
> +	__tlbi_sync_s1ish_kernel();
>  	isb();
>  }

The commit message is correct that flush_tlb_all() is only used for
kernel mappings today, via flush_tlb_kernel_range(), so this is safe.

However, the big comment block around line 200 says:

	flush_tlb_all()
		Invalidate the entire TLB (kernel + user) on all CPUs

... and:

	local_flush_tlb_all()
		Same as flush_tlb_all(), but only applies to the calling CPU.

... where the latter is used for user mappings (upon ASID overflow), so
I think there's some risk of future confusion.

To minimize the risk that flush_tlb_all() gets used for user mappings in
future, how about we rename flush_tlb_all() => flush_tlb_kernel_all(), and
update those comments:

	flush_tlb_kernel_all()
		Invalidate all kernel mappings on all CPUs.
		Should not be used to invalidate user mappings.

	local_flush_tlb_all()
		Invalidate all (kernel + user) mappings on the calling CPU.

Note: I chose flush_tlb_kernel_all() rather than flush_tlb_all_kernel()
__flush_tlb_kernel_{pgtable,range}, with 'kernel' before the operation/scope.

Thanks,
Mark.

> @@ -568,7 +574,7 @@ static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end
>  	dsb(ishst);
>  	__flush_tlb_range_op(vaale1is, start, pages, stride, 0,
>  			     TLBI_TTL_UNKNOWN, false, lpa2_is_enabled());
> -	__tlbi_sync_s1ish();
> +	__tlbi_sync_s1ish_kernel();
>  	isb();
>  }
>  
> @@ -582,7 +588,7 @@ static inline void __flush_tlb_kernel_pgtable(unsigned long kaddr)
>  
>  	dsb(ishst);
>  	__tlbi(vaae1is, addr);
> -	__tlbi_sync_s1ish();
> +	__tlbi_sync_s1ish_kernel();
>  	isb();
>  }
>