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    Subject[tip:x86/urgent] x86, apic: Map the local apic when parsing the MP table.
    Commit-ID:  5989cd6a1cbf86587edcc856791f960978087311
    Author: Eric W. Biederman <>
    AuthorDate: Wed, 4 Aug 2010 13:30:27 -0700
    Committer: H. Peter Anvin <>
    CommitDate: Thu, 5 Aug 2010 16:26:42 -0700

    x86, apic: Map the local apic when parsing the MP table.

    This fixes a regression in 2.6.35 from 2.6.34, that is
    present for select models of Intel cpus when people are
    using an MP table.

    The commit cf7500c0ea133d66f8449d86392d83f840102632
    "x86, ioapic: In mpparse use mp_register_ioapic" started
    calling mp_register_ioapic from MP_ioapic_info. An extremely
    simple change that was obviously correct. Unfortunately
    mp_register_ioapic did just a little more than the previous
    hand crafted code and so we gained this call path.

    The problem call path is:

    Which turned out to be a problem because the local apic
    was not mapped, at that point, unlike the similar point
    in the ACPI parsing code.

    This problem is fixed by mapping the local apic when
    parsing the mptable as soon as we reasonably can.

    Looking at the number of places we setup the fixmap for
    the local apic, I see some serious simplification opportunities.
    For the moment except for not duplicating the setting up of the
    fixmap in init_apic_mappings, I have not acted on them.

    The regression from 2.6.34 is tracked in bug

    Cc: <> 2.6.35
    Reported-by: David Hill <>
    Reported-by: Tvrtko Ursulin <>
    Tested-by: Tvrtko Ursulin <>
    Signed-off-by: Eric W. Biederman <>
    LKML-Reference: <>
    Signed-off-by: H. Peter Anvin <>
    arch/x86/kernel/apic/apic.c | 2 +-
    arch/x86/kernel/mpparse.c | 16 ++++++++++++++++
    2 files changed, 17 insertions(+), 1 deletions(-)

    diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
    index a96489e..c07e513 100644
    --- a/arch/x86/kernel/apic/apic.c
    +++ b/arch/x86/kernel/apic/apic.c
    @@ -1606,7 +1606,7 @@ void __init init_apic_mappings(void)
    * acpi lapic path already maps that address in
    * acpi_register_lapic_address()
    - if (!acpi_lapic)
    + if (!acpi_lapic && !smp_found_config)
    set_fixmap_nocache(FIX_APIC_BASE, apic_phys);

    apic_printk(APIC_VERBOSE, "mapped APIC to %08lx (%08lx)\n",
    diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
    index d86dbf7..d7b6f7f 100644
    --- a/arch/x86/kernel/mpparse.c
    +++ b/arch/x86/kernel/mpparse.c
    @@ -274,6 +274,18 @@ static void __init smp_dump_mptable(struct mpc_table *mpc, unsigned char *mpt)

    void __init default_smp_read_mpc_oem(struct mpc_table *mpc) { }

    +static void __init smp_register_lapic_address(unsigned long address)
    + mp_lapic_addr = address;
    + set_fixmap_nocache(FIX_APIC_BASE, address);
    + if (boot_cpu_physical_apicid == -1U) {
    + boot_cpu_physical_apicid = read_apic_id();
    + apic_version[boot_cpu_physical_apicid] =
    + GET_APIC_VERSION(apic_read(APIC_LVR));
    + }
    static int __init smp_read_mpc(struct mpc_table *mpc, unsigned early)
    char str[16];
    @@ -295,6 +307,10 @@ static int __init smp_read_mpc(struct mpc_table *mpc, unsigned early)
    if (early)
    return 1;

    + /* Initialize the lapic mapping */
    + if (!acpi_lapic)
    + smp_register_lapic_address(mpc->lapic);
    if (mpc->oemptr)

     \ /
      Last update: 2010-08-06 02:19    [W:0.027 / U:10.120 seconds]
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