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    Subject[tip:x86/mm] x86/mtrr: Fix PAT init handling when MTRR is disabled
    Commit-ID:  ad025a73f0e9344ac73ffe1b74c184033e08e7d5
    Gitweb: http://git.kernel.org/tip/ad025a73f0e9344ac73ffe1b74c184033e08e7d5
    Author: Toshi Kani <toshi.kani@hpe.com>
    AuthorDate: Wed, 23 Mar 2016 15:42:01 -0600
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Tue, 29 Mar 2016 12:23:26 +0200

    x86/mtrr: Fix PAT init handling when MTRR is disabled

    get_mtrr_state() calls pat_init() on BSP even if MTRR is disabled.
    This results in calling pat_init() on BSP only since APs do not call
    pat_init() when MTRR is disabled. This inconsistency between BSP
    and APs leads to undefined behavior.

    Make BSP's calling condition to pat_init() consistent with AP's,
    mtrr_ap_init() and mtrr_aps_init().

    Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
    Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Luis R. Rodriguez <mcgrof@suse.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Toshi Kani <toshi.kani@hp.com>
    Cc: elliott@hpe.com
    Cc: konrad.wilk@oracle.com
    Cc: paul.gortmaker@windriver.com
    Cc: xen-devel@lists.xenproject.org
    Link: http://lkml.kernel.org/r/1458769323-24491-6-git-send-email-toshi.kani@hpe.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/cpu/mtrr/generic.c | 24 ++++++++++++++----------
    arch/x86/kernel/cpu/mtrr/main.c | 3 +++
    arch/x86/kernel/cpu/mtrr/mtrr.h | 1 +
    3 files changed, 18 insertions(+), 10 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
    index 19f5736..8d7a29e 100644
    --- a/arch/x86/kernel/cpu/mtrr/generic.c
    +++ b/arch/x86/kernel/cpu/mtrr/generic.c
    @@ -444,11 +444,24 @@ static void __init print_mtrr_state(void)
    pr_debug("TOM2: %016llx aka %lldM\n", mtrr_tom2, mtrr_tom2>>20);
    }

    +/* PAT setup for BP. We need to go through sync steps here */
    +void __init mtrr_bp_pat_init(void)
    +{
    + unsigned long flags;
    +
    + local_irq_save(flags);
    + prepare_set();
    +
    + pat_init();
    +
    + post_set();
    + local_irq_restore(flags);
    +}
    +
    /* Grab all of the MTRR state for this CPU into *state */
    bool __init get_mtrr_state(void)
    {
    struct mtrr_var_range *vrs;
    - unsigned long flags;
    unsigned lo, dummy;
    unsigned int i;

    @@ -481,15 +494,6 @@ bool __init get_mtrr_state(void)

    mtrr_state_set = 1;

    - /* PAT setup for BP. We need to go through sync steps here */
    - local_irq_save(flags);
    - prepare_set();
    -
    - pat_init();
    -
    - post_set();
    - local_irq_restore(flags);
    -
    return !!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED);
    }

    diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
    index 8b1947b..7d393ec 100644
    --- a/arch/x86/kernel/cpu/mtrr/main.c
    +++ b/arch/x86/kernel/cpu/mtrr/main.c
    @@ -752,6 +752,9 @@ void __init mtrr_bp_init(void)
    /* BIOS may override */
    __mtrr_enabled = get_mtrr_state();

    + if (mtrr_enabled())
    + mtrr_bp_pat_init();
    +
    if (mtrr_cleanup(phys_addr)) {
    changed_by_mtrr_cleanup = 1;
    mtrr_if->set_all();
    diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
    index 951884d..6c7ced0 100644
    --- a/arch/x86/kernel/cpu/mtrr/mtrr.h
    +++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
    @@ -52,6 +52,7 @@ void set_mtrr_prepare_save(struct set_mtrr_context *ctxt);
    void fill_mtrr_var_range(unsigned int index,
    u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi);
    bool get_mtrr_state(void);
    +void mtrr_bp_pat_init(void);

    extern void set_mtrr_ops(const struct mtrr_ops *ops);

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