linux-kernel - Re: [PATCH 03/17] arm64: Allow checking of a CPU-local erratum

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Message-ID: <8b6c1423-ad78-0f51-7134-a1062791577f@arm.com>
Date:   Mon, 20 Mar 2017 14:09:16 +0000
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Scott Wood <oss@...error.net>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Ding Tianhong <dingtianhong@...wei.com>
Subject: Re: [PATCH 03/17] arm64: Allow checking of a CPU-local erratum

On 20/03/17 13:56, Mark Rutland wrote:
> On Mon, Mar 06, 2017 at 11:26:08AM +0000, Marc Zyngier wrote:
>> this_cpu_has_cap() only checks the feature array, and not the errata
>> one. In order to be able to check for a CPU-local erratum, allow it
>> to inspect the latter as well.
>>
>> This is consistent with cpus_have_cap()'s behaviour, which includes
>> errata already.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>
> This sounds sensible to me.
>
> Suzuki, any comments?

Yes, this looks fine to me.

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

>
> Thanks,
> Mark.
>
>> ---
>>  arch/arm64/kernel/cpufeature.c | 13 +++++++++++--
>>  1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index abda8e861865..6eb77ae99b79 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -1090,20 +1090,29 @@ static void __init setup_feature_capabilities(void)
>>   * Check if the current CPU has a given feature capability.
>>   * Should be called from non-preemptible context.
>>   */
>> -bool this_cpu_has_cap(unsigned int cap)
>> +static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array,
>> +			       unsigned int cap)
>>  {
>>  	const struct arm64_cpu_capabilities *caps;
>>
>>  	if (WARN_ON(preemptible()))
>>  		return false;
>>
>> -	for (caps = arm64_features; caps->desc; caps++)
>> +	for (caps = cap_array; caps->desc; caps++)
>>  		if (caps->capability == cap && caps->matches)
>>  			return caps->matches(caps, SCOPE_LOCAL_CPU);
>>
>>  	return false;
>>  }
>>
>> +extern const struct arm64_cpu_capabilities arm64_errata[];
>> +
>> +bool this_cpu_has_cap(unsigned int cap)
>> +{
>> +	return (__this_cpu_has_cap(arm64_features, cap) ||
>> +		__this_cpu_has_cap(arm64_errata, cap));
>> +}
>> +
>>  void __init setup_cpu_features(void)
>>  {
>>  	u32 cwg;
>> --
>> 2.11.0
>>