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    Subject[tip:x86/apic] x86, irq: Prefer assigned ID in APIC ID register for x86_64
    Commit-ID:  b141cb5363583a887ab2d6f742bc849f615634ff
    Gitweb: http://git.kernel.org/tip/b141cb5363583a887ab2d6f742bc849f615634ff
    Author: Yinghai Lu <yinghai@kernel.org>
    AuthorDate: Mon, 27 Oct 2014 13:21:40 +0800
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Mon, 3 Nov 2014 11:56:07 +0100

    x86, irq: Prefer assigned ID in APIC ID register for x86_64

    Perfer the assigned ID in APIC ID register for x86_64 if it's still
    available.

    [ tglx: Added comments ]

    Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Joerg Roedel <joro@8bytes.org>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
    Cc: Bjorn Helgaas <bhelgaas@google.com>
    Cc: Randy Dunlap <rdunlap@infradead.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Grant Likely <grant.likely@linaro.org>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Link: http://lkml.kernel.org/r/1414387308-27148-11-git-send-email-jiang.liu@linux.intel.com
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/kernel/apic/io_apic.c | 45 ++++++++++++++++++++++++++++++++++++------
    1 file changed, 39 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
    index acaee90..02212fb 100644
    --- a/arch/x86/kernel/apic/io_apic.c
    +++ b/arch/x86/kernel/apic/io_apic.c
    @@ -3580,26 +3580,59 @@ static int __init io_apic_get_unique_id(int ioapic, int apic_id)
    return apic_id;
    }

    -static u8 __init io_apic_unique_id(u8 id)
    +static u8 __init io_apic_unique_id(int idx, u8 id)
    {
    if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
    !APIC_XAPIC(apic_version[boot_cpu_physical_apicid]))
    - return io_apic_get_unique_id(nr_ioapics, id);
    + return io_apic_get_unique_id(idx, id);
    else
    return id;
    }
    #else
    -static u8 __init io_apic_unique_id(u8 id)
    +static u8 __init io_apic_unique_id(int idx, u8 id)
    {
    - int i;
    + union IO_APIC_reg_00 reg_00;
    DECLARE_BITMAP(used, 256);
    + unsigned long flags;
    + u8 new_id;
    + int i;

    bitmap_zero(used, 256);
    for_each_ioapic(i)
    __set_bit(mpc_ioapic_id(i), used);
    +
    + /* Hand out the requested id if available */
    if (!test_bit(id, used))
    return id;
    - return find_first_zero_bit(used, 256);
    +
    + /*
    + * Read the current id from the ioapic and keep it if
    + * available.
    + */
    + raw_spin_lock_irqsave(&ioapic_lock, flags);
    + reg_00.raw = io_apic_read(idx, 0);
    + raw_spin_unlock_irqrestore(&ioapic_lock, flags);
    + new_id = reg_00.bits.ID;
    + if (!test_bit(new_id, used)) {
    + apic_printk(APIC_VERBOSE, KERN_INFO
    + "IOAPIC[%d]: Using reg apic_id %d instead of %d\n",
    + idx, new_id, id);
    + return new_id;
    + }
    +
    + /*
    + * Get the next free id and write it to the ioapic.
    + */
    + new_id = find_first_zero_bit(used, 256);
    + reg_00.bits.ID = new_id;
    + raw_spin_lock_irqsave(&ioapic_lock, flags);
    + io_apic_write(idx, 0, reg_00.raw);
    + reg_00.raw = io_apic_read(idx, 0);
    + raw_spin_unlock_irqrestore(&ioapic_lock, flags);
    + /* Sanity check */
    + BUG_ON(reg_00.bits.ID != new_id);
    +
    + return new_id;
    }
    #endif

    @@ -3865,7 +3898,7 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base,
    return;
    }

    - ioapics[idx].mp_config.apicid = io_apic_unique_id(id);
    + ioapics[idx].mp_config.apicid = io_apic_unique_id(idx, id);
    ioapics[idx].mp_config.apicver = io_apic_get_version(idx);

    /*

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