Re: [PATCH v6 08/11] arm64: mm: Avoid TLBI when marking pages as valid

[Suzuki K Poulose]

On 04/10/2024 15:43, Steven Price wrote:
> When __change_memory_common() is purely setting the valid bit on a PTE
> (e.g. via the set_memory_valid() call) there is no need for a TLBI as
> either the entry isn't changing (the valid bit was already set) or the
> entry was invalid and so should not have been cached in the TLB.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>


> ---
> v4: New patch
> ---
>   arch/arm64/mm/pageattr.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 0e270a1c51e6..547a9e0b46c2 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -60,7 +60,13 @@ static int __change_memory_common(unsigned long start, unsigned long size,
>   	ret = apply_to_page_range(&init_mm, start, size, change_page_range,
>   					&data);
>   
> -	flush_tlb_kernel_range(start, start + size);
> +	/*
> +	 * If the memory is being made valid without changing any other bits
> +	 * then a TLBI isn't required as a non-valid entry cannot be cached in
> +	 * the TLB.
> +	 */
> +	if (pgprot_val(set_mask) != PTE_VALID || pgprot_val(clear_mask))
> +		flush_tlb_kernel_range(start, start + size);
>   	return ret;
>   }
>