Re: [PATCH 02/16] arm64: Move errata work around check on boot CPU

From: Suzuki K Poulose <Suzuki.Poulose@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com,
	ckadabi@codeaurora.org, ard.biesheuvel@linaro.org,
	marc.zyngier@arm.com, catalin.marinas@arm.com,
	will.deacon@arm.com, linux-kernel@vger.kernel.org,
	jnair@caviumnetworks.com
Subject: Re: [PATCH 02/16] arm64: Move errata work around check on boot CPU
Date: Tue, 23 Jan 2018 15:07:18 +0000	[thread overview]
Message-ID: <31e6c173-9c27-80fd-a24e-8d234bb4be01@arm.com> (raw)
In-Reply-To: <20180123145934.GS22781@e103592.cambridge.arm.com>

On 23/01/18 14:59, Dave Martin wrote:
> On Tue, Jan 23, 2018 at 12:27:55PM +0000, Suzuki K Poulose wrote:
>> We trigger CPU errata work around check on the boot CPU from
>> smp_prepare_boot_cpu() to make sure that we run the checks only
>> after the CPU feature infrastructure is initialised.
> 
> On the surface of it, this sounds like a bug fix.

No, this is not. It is just moving the code to cpufeature.c

Earlier it was :

smp_prepare_boot_cpu()  -> cpuinfo_store_boot_cpu() -> init_cpu_features()

and then we did update_cpu_errata_workarounds() after we have done
cpuinfo_store_boot_cpu(). With this change we do :

smp_prepare_boot_cpu()  -> cpuinfo_store_boot_cpu() -> init_cpu_features() -> update_cpu_errata_workarounds()

> 
> Should there be a Fixes tag if so?
> 
> If this reordering doesn't matter for upstream, it would be good to have
> a quick explanation here as to why not.

Sure, will make it clearer.

Cheers
Suzuki

> 
> Cheers
> ---Dave
> 
>>
>> We can do this from init_cpu_features() which is called only
>> on the boot CPU and does the initilisation of the infrastructure.
>> As we are consolidating the cpu capability handling, let us
>> move this to where it should belong. No functional changes.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>>   arch/arm64/kernel/cpufeature.c | 6 ++++++
>>   arch/arm64/kernel/smp.c        | 6 ------
>>   2 files changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index 6a8dfdc532b1..ebb467340b9c 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -545,6 +545,12 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
>>   		init_cpu_ftr_reg(SYS_ZCR_EL1, info->reg_zcr);
>>   		sve_init_vq_map();
>>   	}
>> +
>> +	/*
>> +	 * Run the errata work around checks on the boot CPU, once we have
>> +	 * initialised the cpu feature infrastructure.
>> +	 */
>> +	update_cpu_errata_workarounds();
>>   }
>>   
>>   static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new)
>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>> index 3b8ad7be9c33..5cef11450183 100644
>> --- a/arch/arm64/kernel/smp.c
>> +++ b/arch/arm64/kernel/smp.c
>> @@ -448,12 +448,6 @@ void __init smp_prepare_boot_cpu(void)
>>   	jump_label_init();
>>   	cpuinfo_store_boot_cpu();
>>   	save_boot_cpu_run_el();
>> -	/*
>> -	 * Run the errata work around checks on the boot CPU, once we have
>> -	 * initialised the cpu feature infrastructure from
>> -	 * cpuinfo_store_boot_cpu() above.
>> -	 */
>> -	update_cpu_errata_workarounds();
>>   }
>>   
>>   static u64 __init of_get_cpu_mpidr(struct device_node *dn)
>> -- 
>> 2.13.6
>>
>>
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