[PATCH v4 3/5] arm64: Add support for FEAT_HAFT

[Yicong Yang]

On 2024/11/5 10:47, Yicong Yang wrote:
> On 2024/11/5 1:28, Catalin Marinas wrote:
>> On Sat, Nov 02, 2024 at 06:42:33PM +0800, Yicong Yang wrote:
>>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>>> index 3d261cc123c1..ed8c784ca082 100644
>>> --- a/arch/arm64/include/asm/cpufeature.h
>>> +++ b/arch/arm64/include/asm/cpufeature.h
>>> @@ -838,6 +838,12 @@ static inline bool system_supports_poe(void)
>>>  		alternative_has_cap_unlikely(ARM64_HAS_S1POE);
>>>  }
>>>  
>>> +static inline bool system_supports_haft(void)
>>> +{
>>> +	return IS_ENABLED(CONFIG_ARM64_HAFT) &&
>>> +		cpus_have_final_cap(ARM64_HAFT);
>>> +}
>>
>> I'm fine with this approach. If we ever get hardware with mismatched
>> FEAT_HAFT and some secondary CPUs don't come up, we can revisit.
>>
>>> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
>>> index ccbae4525891..0bc88df7cb35 100644
>>> --- a/arch/arm64/mm/proc.S
>>> +++ b/arch/arm64/mm/proc.S
>>> @@ -498,6 +498,10 @@ alternative_else_nop_endif
>>>  	and	x9, x9, ID_AA64MMFR1_EL1_HAFDBS_MASK
>>>  	cbz	x9, 1f
>>>  	orr	tcr, tcr, #TCR_HA		// hardware Access flag update
>>> +
>>> +#ifdef CONFIG_ARM64_HAFT
>>> +	orr	tcr2, tcr2, TCR2_EL1x_HAFT
>>> +#endif /* CONFIG_ARM64_HAFT */
>>>  1:
>>>  #endif	/* CONFIG_ARM64_HW_AFDBM */
>>>  	msr	mair_el1, mair
>>
>> If you still want #ifdefs, I'd have left it outside the HW_AFDBM. We
>> already have a dependency in the Kconfig. Anyway, I can fix this up.
> 
> yes it has already depend on the HW_AFDBM. And one asm won't cause much to the
> Image size if user want CONFIG_ARM64_HAFT=n. I'll drop the #ifdef here.
> 

I rethink it and maybe we still need the #ifdef here considering one case: the hardware
supports FEAT_HAFT while user make CONFIG_ARM64_HAFT=n, in such case the HAFT will be
enabled unexpectedly if no CONFIG_ARM64_HAFT protection here.

Thanks.