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    Subject[PATCH 4.8 058/138] x86/smpboot: Init apic mapping before usage
    Date
    4.8-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thomas Gleixner <tglx@linutronix.de>

    commit 1e90a13d0c3dc94512af1ccb2b6563e8297838fa upstream.

    The recent changes, which forced the registration of the boot cpu on UP
    systems, which do not have ACPI tables, have been fixed for systems w/o
    local APIC, but left a wreckage for systems which have neither ACPI nor
    mptables, but the CPU has an APIC, e.g. virtualbox.

    The boot process crashes in prefill_possible_map() as it wants to register
    the boot cpu, which needs to access the local apic, but the local APIC is
    not yet mapped.

    There is no reason why init_apic_mapping() can't be invoked before
    prefill_possible_map(). So instead of playing another silly early mapping
    game, as the ACPI/mptables code does, we just move init_apic_mapping()
    before the call to prefill_possible_map().

    In hindsight, I should have noticed that combination earlier.

    Sorry for the churn (also in stable)!

    Fixes: ff8560512b8d ("x86/boot/smp: Don't try to poke disabled/non-existent APIC")
    Reported-and-debugged-by: Michal Necasek <michal.necasek@oracle.com>
    Reported-and-tested-by: Wolfgang Bauer <wbauer@tmo.at>
    Cc: prarit@redhat.com
    Cc: ville.syrjala@linux.intel.com
    Cc: michael.thayer@oracle.com
    Cc: knut.osmundsen@oracle.com
    Cc: frank.mehnert@oracle.com
    Cc: Borislav Petkov <bp@alien8.de>
    Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1610282114380.5053@nanos
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/setup.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/arch/x86/kernel/setup.c
    +++ b/arch/x86/kernel/setup.c
    @@ -1222,11 +1222,16 @@ void __init setup_arch(char **cmdline_p)
    if (smp_found_config)
    get_smp_config();

    + /*
    + * Systems w/o ACPI and mptables might not have it mapped the local
    + * APIC yet, but prefill_possible_map() might need to access it.
    + */
    + init_apic_mappings();
    +
    prefill_possible_map();

    init_cpu_to_node();

    - init_apic_mappings();
    io_apic_init_mappings();

    kvm_guest_init();

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