Re: [tip:x86/apic] x86/acpi: Introduce persistent storage for cpuid <-> apicid mapping

[Dou Liyang]

Hi tglx,

At 10/07/2016 09:00 PM, Thomas Gleixner wrote:
> On Fri, 7 Oct 2016, Thomas Gleixner wrote:
> > On Fri, 7 Oct 2016, Dou Liyang wrote:
> > > Is it possible that the "-1/oxffffffff" could appear in the MADT which is one
> > > of the ACPI tables?
> >
> > According to the SDM the x2apic id is a 32bit ID, so 0xffffffff is a
> > legitimate value.

Yes, I see.

> The ACPI spec says that bit 0 of the x2apic flags field tells whether the
> logical processor is present or not. So the proper check for x2apic is that
> flag.
>
> The lapic structure has the same flag, but the kernel ignores the flags for
> both lapic and x2apic.

It seems the kernel uses the flags in this sentence:

	enabled = processor->lapic_flags & ACPI_MADT_ENABLED;


> I'm going to apply the minimal fix of checking for id == 0xff in
> acpi_lapic_parse() for now, but this needs to be revisited and fixed
> proper.

Yes, I will do it.


Thanks

	Dou.