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    SubjectPATCH: Update disable_IO_APIC to use 8-bit destination field (X86_64)
    On the Unisys ES7000/ONE system, we encountered a problem where
    performing a kexec reboot or dump on any cell other than cell 0 causes
    the system timer to stop working, resulting in a hang during timer
    calibration in the new kernel.

    We traced the problem to one line of code in disable_IO_APIC(), which
    needs to restore the timer's IO-APIC configuration before rebooting. The
    code is currently using the 4-bit physical destination field, rather
    than using the 8-bit logical destination field, and it cuts off the
    upper 4 bits of the timer's APIC ID. If we change this to use the
    logical destination field, the timer works and we can kexec on the upper
    cells. This was tested on two different cells (0 and 2) in an ES7000/ONE

    For reference, the relevant Intel xAPIC spec is kept at,
    specifically on page 334.

    -- Ben

    --- linux- 2007-01-10
    14:10:37.000000000 -0500
    +++ linux- 2007-01-17
    09:20:24.000000000 -0500
    @@ -1261,7 +1261,7 @@
    entry.dest_mode = 0; /* Physical */
    entry.delivery_mode = dest_ExtINT; /* ExtInt */
    entry.vector = 0;
    - entry.dest.physical.physical_dest =
    + entry.dest.logical.logical_dest =


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