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    SubjectRe: [PATCH 23/23] x86, PCI: add pcibios_root_rescan
    On Tue, Mar 6, 2012 at 11:29 PM, Yinghai Lu <yinghai@kernel.org> wrote:
    > On Tue, Mar 6, 2012 at 7:49 PM, Bjorn Helgaas <bjorn.helgaas@gmail.com> wrote:
    >
    >>> my sandbridge system has cpu bus 0x7f, and 0xff in DSDT.
    >>>
    >>> but nehalem and westmere system does not have cpu bus 0xf8, ... 0xff.
    >>
    >> I think you're saying that on some machines, the BIOS decided not to
    >> expose host bridges leading to CPU devices, and you want to discover
    >> those devices anyway.  (What's the reason you want to discover them?)
    >
    > current code for mmconf will set pcibios_last_bios according to mmconf
    > bus range.
    >
    > so it legacy peer root bus fix up will discover those cpu buses.
    >
    > then if some one remove them through
    > echo 1 > /sys/devices/pci0000:ff/pci_bus/0000:ff/remove
    >
    > then
    >
    > echo 1 > /sys/bus/pci/rescan_root
    >
    > will not recover those cpu buses without this patch.

    What's the reason we need to discover those CPU devices in the first place?

    I don't think the current policy of blindly probing for things should
    be continued forever.
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