[PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

Hanjun Guo hanjun.guo at linaro.org
Tue Sep 9 09:00:34 PDT 2014

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.


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