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    SubjectRe: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id
    Ingo Molnar wrote:
    > * Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
    >
    >> On Mon, Aug 24, 2009 at 10:12:01PM -0700, Yinghai Lu wrote:
    >>> Ravikiran G Thirumalai wrote:
    >>>> On Mon, Aug 24, 2009 at 04:53:45PM -0700, Yinghai Lu wrote:
    >>>>> Ravikiran G Thirumalai wrote:
    >>>>>> Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
    >>>>>> Cc: Yinghai Lu <yinghai@kernel.org>
    >>>>>>
    >>>> Why? The specs seem to indicate otherwise unless I am mistaken --
    >>>> Intel systems programming guide, Vol 3A Part1, chapter 7 section
    >>>> 7.5.5 - Identifying Logical Processors in a MP system:
    >>>> <quote>
    >>>> After the BIOS has completed the MP initialization protocol, each logical
    >>>> processor can be uniquely identified by its local APIC ID. Software can
    >>>> access these APIC IDs in either of the following ways
    >>>> </quote>
    >>>> phys_pkg_id() indicates that the logical package id is being looked up,
    >>>> so local apic id should be used here no?
    >>>> What am I missing?
    >>> initial apic id : it can not changed, there is fixed mapping from that to physical processor id aka socket id / node id.
    >>>
    >>> apic id: could be changed by BIOS to any value. there is no good way to get phys_pkg_id from that.
    >>>
    >> But BIOS is supposed to change it to a sane value. Until 2.6.30,
    >> local apic id has been used to get phys_pkg_id for the 'flat'
    >> apics! What changed? Was this changed for a BIOS bug? Even the
    >> intel books seem to indicate local apic usage!
    >
    > We should revert to the .30 behavior unless there's a good reason
    > (even in that case we'll solve the regression and do a workaround
    > for vSMP). Yinghai?

    we should stop overloading phys_pkg_id to get physical processor id (socket id ?) and apic id.

    we need to find out what vSMP initial apic id looks like. and have one better phys_pkg_id for it.

    otherwise we have problem with intel system that have apic id changing by BIOS too.

    YH


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