linux-kernel - Re: [PATCH v2 12/22] arm64: Delay cpu feature checks

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Message-ID: <561CD918.7000107@arm.com>
Date:	Tue, 13 Oct 2015 11:12:40 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	Vladimir.Murzin@....com, steve.capper@...aro.org,
	ard.biesheuvel@...aro.org, marc.zyngier@....com,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	edward.nevill@...aro.org, aph@...hat.com, james.morse@....com,
	andre.przywara@....com, dave.martin@....com
Subject: Re: [PATCH v2 12/22] arm64: Delay cpu feature checks

On 08/10/15 12:08, Catalin Marinas wrote:
> On Mon, Oct 05, 2015 at 06:02:01PM +0100, Suzuki K. Poulose wrote:
>> +	/*
>> +	 * second pass allows enable() invoked on active each CPU
>> +	 * to consider interacting capabilities.
>> +	 */
>
> This comment doesn't read properly.
>

Fixed locally

>> +	/*XXX: Are we really safe to call printk here ? */
>> +	pr_crit("FATAL: CPU%d is missing %s : %s \n",
>> +			smp_processor_id(), cap_type, cap->desc);
>
> I'm not sure it's safe either, basically we haven't fully brought the
> CPU into the system.

Btw, we already print "Booted secondary cpu" from secondary_start_kernel()
before we trigger the notifiers. So I think it should be safe to call it
at the moment.

>
>> +	asm volatile(
>> +			" 1:	wfe \n\t"
>> +			"	b 1b\n"
>> +		    );
>> +}
>
> We could add a wfi as well in the mix.
>
> However, if we have PSCI, we should use it to park the CPUs back into
> firmware (via cpu_operations.cpu_die), and only use the above loop if
> that fails.

Added cpu_die() and falls back to the trap as above.


>
>> +/*
>> + * Run through the enabled system capabilities and enable() it on this CPU.
>
> s/it/them/
>

Fixed.

Thanks
Suzuki

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