[PATCH 1/2] arm64: Add support for FEAT_HAFT

[Yicong Yang]

On 2024/8/6 15:57, Marc Zyngier wrote:
> On Tue, 06 Aug 2024 04:09:09 +0100,
> Yicong Yang <yangyicong at huawei.com> wrote:
>>
>>>> +#ifdef CONFIG_ARM64_HAFT
>>>> +	{
>>>> +		.desc = "Hardware managed Access Flag for Table Descriptor",
>>>> +		/*
>>>> +		 * Per Spec, software management of Access Flag for Table
>>>> +		 * descriptor is not supported, so make this feature system
>>>> +		 * wide.
>>>> +		 */
>>>
>>> I don't understand what you mean by this. Can you please clarify?
>>>
>>
>> Since this cannot be managed by the software, we should restrict all the CPUs
>> in the system to have and enable this feature which is indicated by
>> ARM64_CPUCAP_BOOT_CPU_FEATURE. It's not possible for part of the CPUs don't have
>> this feature and managed manually.
>>
>> I make this comment here since it's handled different from what ARM64_HW_DBM does (which
>> is ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE). Maybe it's redundant and can be dropped.
> 
> Ah, I see what you mean. I think this is still important to capture,
> but maybe in a clearer manner. Something like:
> 
> 	Contrary to the page/block access flag, the table access flag
> 	cannot be emulated in software (no access fault will occur).
> 	Therefore mandate that all CPUs have FEAT_HAFT.
> 

Will refine the comment here in v2. Thanks for the suggestion.

Thanks.