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

[Jon Masters]

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.

Jon.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/