linux-kernel - Re: [PATCH v3 1/6] arm64: cpufeature: Allow early detect of specific features

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Date:   Mon, 21 May 2018 13:10:55 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     Daniel Thompson <daniel.thompson@...aro.org>,
        Suzuki K Poulose <Suzuki.Poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        marc.zyngier@....com, mark.rutland@....com,
        christoffer.dall@....com, james.morse@....com, joelaf@...gle.com,
        joel.opensrc@...il.com, catalin.marinas@....com,
        will.deacon@....com
Subject: Re: [PATCH v3 1/6] arm64: cpufeature: Allow early detect of specific
 features



On 21/05/18 13:06, Daniel Thompson wrote:
> On Mon, May 21, 2018 at 12:45:22PM +0100, Suzuki K Poulose wrote:
>> On 21/05/18 12:35, Julien Thierry wrote:
>>> From: Daniel Thompson <daniel.thompson@...aro.org>
>>>
>>> Currently it is not possible to detect features of the boot CPU
>>> until the other CPUs have been brought up.
>>>
>>> This prevents us from reacting to features of the boot CPU until
>>> fairly late in the boot process. To solve this we allow a subset
>>> of features (that are likely to be common to all clusters) to be
>>> detected based on the boot CPU alone.
>>>
>>> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
>>> [julien.thierry@....com: check non-boot cpu missing early features, avoid
>>> 			 duplicates between early features and normal
>>> 			 features]
>>> Signed-off-by: Julien Thierry <julien.thierry@....com>
>>> Cc: Catalin Marinas <catalin.marinas@....com>
>>> Cc: Will Deacon <will.deacon@....com>
>>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>>
>> nit: Since this is completely different from what Daniel started with,
>> you could simply reset the author to yourself. The boot CPU feature was
>> added keeping this user in mind.
> 
> Agree! It's no longer my patch.
> 
> If you want to retain any credit than Suggested-by: would make quite
> sufficient.
> 

Good point, I didn't think of that.

I'll change this after I get other reviews for this version.

Thanks,

> 
>>
>> The patch as such looks good to me.
>>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>>
>>> ---
>>>    arch/arm64/kernel/cpufeature.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>>> index 9d1b06d..e03e897 100644
>>> --- a/arch/arm64/kernel/cpufeature.c
>>> +++ b/arch/arm64/kernel/cpufeature.c
>>> @@ -1030,7 +1030,7 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
>>>    	{
>>>    		.desc = "GIC system register CPU interface",
>>>    		.capability = ARM64_HAS_SYSREG_GIC_CPUIF,
>>> -		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
>>> +		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
>>>    		.matches = has_useable_gicv3_cpuif,
>>>    		.sys_reg = SYS_ID_AA64PFR0_EL1,
>>>    		.field_pos = ID_AA64PFR0_GIC_SHIFT,
>>> --
>>> 1.9.1
>>>
>>

-- 
Julien Thierry