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    Subject[tip:x86/apic] x86/apic: Make disable x2apic work really
    Commit-ID:  9aa16365275a272283acbda665634ca3dc8b46fe
    Gitweb: http://git.kernel.org/tip/9aa16365275a272283acbda665634ca3dc8b46fe
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Thu, 15 Jan 2015 21:22:16 +0000
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Thu, 22 Jan 2015 15:10:54 +0100

    x86/apic: Make disable x2apic work really

    If x2apic_preenabled is not enabled, then disable_x2apic() is not
    called from various places which results in x2apic_disabled not being
    set. So other code pathes can happily reenable the x2apic.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Jiang Liu <jiang.liu@linux.intel.com>
    Cc: Joerg Roedel <joro@8bytes.org>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Link: http://lkml.kernel.org/r/20150115211702.621431109@linutronix.de
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/kernel/apic/apic.c | 14 +++++---------
    1 file changed, 5 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
    index 08144f5..fdc6c60 100644
    --- a/arch/x86/kernel/apic/apic.c
    +++ b/arch/x86/kernel/apic/apic.c
    @@ -1479,8 +1479,6 @@ static bool nox2apic __initdata;

    #ifdef CONFIG_X86_X2APIC
    int x2apic_mode;
    -/* x2apic enabled before OS handover */
    -static int x2apic_preenabled;
    static int x2apic_disabled;
    static int __init setup_nox2apic(char *str)
    {
    @@ -1535,18 +1533,19 @@ static __init void disable_x2apic(void)
    setup_clear_cpu_cap(X86_FEATURE_X2APIC);
    }

    - x2apic_disabled = 1;
    x2apic_mode = 0;

    register_lapic_address(mp_lapic_addr);
    }
    +
    + x2apic_disabled = 1;
    }

    void check_x2apic(void)
    {
    if (x2apic_enabled()) {
    pr_info("x2apic enabled by BIOS, switching to x2apic ops\n");
    - x2apic_preenabled = x2apic_mode = 1;
    + x2apic_mode = 1;
    }
    }

    @@ -1569,8 +1568,6 @@ void enable_x2apic(void)
    wrmsrl(MSR_IA32_APICBASE, msr | X2APIC_ENABLE);
    }
    }
    -#else
    -#define x2apic_preenabled (0)
    #endif /* CONFIG_X86_X2APIC */

    static int __init try_to_enable_IR(void)
    @@ -1599,8 +1596,7 @@ static __init void try_to_enable_x2apic(int ir_stat)
    (IS_ENABLED(CONFIG_HYPERVISOR_GUEST) &&
    !hypervisor_x2apic_available())) {
    pr_info("IRQ remapping doesn't support X2APIC mode, disable x2apic.\n");
    - if (x2apic_preenabled)
    - disable_x2apic();
    + disable_x2apic();
    return;
    }

    @@ -1643,7 +1639,7 @@ void __init enable_IR_x2apic(void)
    legacy_pic->mask_all();
    mask_ioapic_entries();

    - if (x2apic_preenabled && nox2apic)
    + if (nox2apic)
    disable_x2apic();
    /* If irq_remapping_prepare() succeded, try to enable it */
    if (ir_stat >= 0)

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