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

From: Yinghai Lu
Date: Fri Oct 07 2016 - 14:55:51 EST

On Fri, Oct 7, 2016 at 6:00 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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.
> 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.
> 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.

Good to me. Thanks for fixing it.