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    Subject[PATCH 5.4 065/408] x86/nmi: Fix nmi_handle() duration miscalculation
    Date
    From: Libing Zhou <libing.zhou@nokia-sbell.com>

    [ Upstream commit f94c91f7ba3ba7de2bc8aa31be28e1abb22f849e ]

    When nmi_check_duration() is checking the time an NMI handler took to
    execute, the whole_msecs value used should be read from the @duration
    argument, not from the ->max_duration, the latter being used to store
    the current maximal duration.

    [ bp: Rewrite commit message. ]

    Fixes: 248ed51048c4 ("x86/nmi: Remove irq_work from the long duration NMI handler")
    Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Libing Zhou <libing.zhou@nokia-sbell.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: Changbin Du <changbin.du@gmail.com>
    Link: https://lkml.kernel.org/r/20200820025641.44075-1-libing.zhou@nokia-sbell.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kernel/nmi.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
    index 54c21d6abd5ac..5bb001c0c771a 100644
    --- a/arch/x86/kernel/nmi.c
    +++ b/arch/x86/kernel/nmi.c
    @@ -106,7 +106,6 @@ fs_initcall(nmi_warning_debugfs);

    static void nmi_check_duration(struct nmiaction *action, u64 duration)
    {
    - u64 whole_msecs = READ_ONCE(action->max_duration);
    int remainder_ns, decimal_msecs;

    if (duration < nmi_longest_ns || duration < action->max_duration)
    @@ -114,12 +113,12 @@ static void nmi_check_duration(struct nmiaction *action, u64 duration)

    action->max_duration = duration;

    - remainder_ns = do_div(whole_msecs, (1000 * 1000));
    + remainder_ns = do_div(duration, (1000 * 1000));
    decimal_msecs = remainder_ns / 1000;

    printk_ratelimited(KERN_INFO
    "INFO: NMI handler (%ps) took too long to run: %lld.%03d msecs\n",
    - action->handler, whole_msecs, decimal_msecs);
    + action->handler, duration, decimal_msecs);
    }

    static int nmi_handle(unsigned int type, struct pt_regs *regs)
    --
    2.25.1


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