linux-kernel - Re: [PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

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Date:	Wed, 10 Sep 2014 00:14:29 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Jon Masters <jcm@...hat.com>
CC:	Catalin Marinas <catalin.marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <mark.rutland@....com>,
	Olof Johansson <olof@...om.net>,
	Grant Likely <grant.likely@...aro.org>,
	linaro-acpi@...ts.linaro.org, Liviu Dudau <Liviu.Dudau@....com>,
	Lv Zheng <lv.zheng@...el.com>, Rob Herring <robh@...nel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Robert Moore <robert.moore@...el.com>,
	linux-acpi@...r.kernel.org, Charles.Garcia-Tobin@....com,
	Robert Richter <rric@...nel.org>,
	Jason Cooper <jason@...edaemon.net>,
	Arnd Bergmann <arnd@...db.de>,
	Marc Zyngier <marc.zyngier@....com>,
	Will Deacon <will.deacon@....com>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	linux-kernel@...r.kernel.org, Sudeep Holla <Sudeep.Holla@....com>
Subject: Re: [PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

On 2014年09月10日 00:04, Jon Masters wrote:
> On 09/09/2014 12:00 PM, Hanjun Guo wrote:
>> On 2014年09月09日 13:44, Jon Masters wrote:
>>> On 09/09/2014 12:57 AM, Hanjun Guo wrote:
>>>> Hi Jon,
>>>>
>>>> On 2014年09月09日 12:23, Jon Masters wrote:
>>>>> On 09/01/2014 10:57 AM, Hanjun Guo wrote:
>>>>>> MADT contains the information for MPIDR which is essential for
>>>>>> SMP initialization, parse the GIC cpu interface structures to
>>>>>> get the MPIDR value and map it to cpu_logical_map(), and add
>>>>>> enabled cpu with valid MPIDR into cpu_possible_map.
>>>>>>
>>>>>> ACPI 5.1 only has two explicit methods to boot up SMP, PSCI and
>>>>>> Parking protocol, but the Parking protocol is only specified for
>>>>>> ARMv7 now, so make PSCI as the only way for the SMP boot protocol
>>>>>> before some updates for the ACPI spec or the Parking protocol spec.
>>>>>> +	/* CPU 0 was already initialized */
>>>>>> +	if (cpu) {
>>>>>> +		if (cpu_ops[cpu]->cpu_init(NULL, cpu))
>>>>>> +			return -EOPNOTSUPP;
>>>>>> +
>>>>>> +		/* map the logical cpu id to cpu MPIDR */
>>>>>> +		cpu_logical_map(cpu) = mpidr;
>>>>> I'm not sure it's worth noting in a comment or just in the dialogue that
>>>>> none of these MPIDR values is literally the value in the MPIDR. Linux
>>>>> doesn't store that anyway (even in the cpu_logical_map), since it is
>>>>> pre-filtered against MPIDR_HWID_BITMASK to remove the non-affinity level
>>>>> bits. And since the ACPI5.1 specification requires that non-affinity
>>>>> bits be zero everything works. But it relies upon this assumption so it
>>>>> might be worth explicitly masking out the bits when making the call into:
>>>>>
>>>>>        acpi_map_gic_cpu_interface(processor->arm_mpidr,
>>>>>                processor->flags & ACPI_MADT_ENABLED);
>>>>>
>>>>> During the parsing of the processor object's MPIDR value.
>>>> Yes, I agree with you. When I tested this patch set on our
>>>> ARM64 platform, I found this problem too. some firmware
>>>> will just present the real MPIDR value to OS which some reserved
>>>> bit set to 1, and it will lead to some logic problem in this patch.
>>>> (actually firmware didn't obey with ACPI spec)
>>>>
>>>> I had updated the patch with:
>>>>
>>>> +	acpi_map_gic_cpu_interface(processor->arm_mpidr & MPIDR_HWID_BITMASK,
>>>> +		processor->flags & ACPI_MADT_ENABLED);
>>>>
>>>> and then the problem was gone :)
>>> Did I miss an updated patch posting then? It is possible...
>> No, you didn't miss it, I'm still working on the new version, sorry I didn't
>> clarify that in my previous email.
> Thanks. If you could copy me on the next posting that would rock. 

Sure I will.

> In a
> few hours we should have another platform posted as an example. In
> addition, a couple of lower priority patches (building upon the core
> ACPI pieces) should be posted as well.

That will be great! :)

Thanks
Hanjun

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