Re: [PATCH v1 2/3] arm64: mm: Handle invalid large leaf mappings correctly

[Kevin Brodsky]

On 23/03/2026 18:25, Ryan Roberts wrote:
>>> @@ -132,11 +137,12 @@ static int __change_memory_common(unsigned long start, unsigned long size,
>>>  	ret = update_range_prot(start, size, set_mask, clear_mask);
>>>  
>>>  	/*
>>> -	 * 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 the memory is being switched from present-invalid to 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))
>>> +	if (pgprot_val(set_mask) != (PTE_MAYBE_NG | PTE_VALID) ||
>> It isn't obvious to understand where all those PTE_MAYBE_NG come from if
>> one hasn't realised that PTE_PRESENT_INVALID overlays PTE_NG.
>>
>> Since for this purpose we always set/clear both PTE_VALID and
>> PTE_MAYBE_NG, maybe we could define some macro as PTE_VALID |
>> PTE_MAYBE_NG, as a counterpart to PTE_PRESENT_INVALID?
> How about:
>
> #define PTE_PRESENT_VALID_KERNEL	(PTE_VALID | PTE_MAYBE_NG)
>
> The user space equivalent has NG clear, so important to clarify that this is the
> kernel value, I think.

Sounds good to me.

- Kevin