Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id

Ravikiran G Thirumalai
2009-08-25T19:28:01Z

On Tue, Aug 25, 2009 at 11:50:56AM -0700, Yinghai Lu wrote:
>Cyrill Gorcunov wrote:
>
>initial apic id and apic id could be different.
>
>and we should use initial apic id to get correct phys pkg id in case BIOS set crazy apic id.
>

Is there a specific bug we are fixing here? Again, this behavior was
present from atleast 2.6.15-2.6.30 on 'flat' and older 'cluster' apics, and intel
documentation suggests local apic be used. Is there a specific bios bug
that is being fixed?

(The BIOS is not supposed to set a crazy apic ID. The BIOS is buggy in that
case -- Quoting section 9.4.6 from Intel System programming guide vol 3A
part 1:

<quote>
9.4.6 Local APIC ID
At power up, system hardware assigns a unique APIC ID to each local APIC on
the system bus (for Pentium 4 and Intel Xeon processors) or on the APIC bus
(for P6 family and Pentium processors). The hardware assigned APIC ID is
based on system topology and includes encoding for socket position and
cluster information (see Figure 7-2).
In MP systems, the local APIC ID is also used as a processor ID by the BIOS
and the operating system....
</quote>)

Thanks,
Kiran