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    SubjectRE: [PATCH] x86/nmi: Fix nmi_handle duration miscalculation
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    Thanks for your comments, I will recommit patch soon.

    -----Original Message-----
    From: peterz@infradead.org <peterz@infradead.org>
    Sent: 2020年8月19日 16:07
    To: Zhou, Libing (NSB - CN/Hangzhou) <libing.zhou@nokia-sbell.com>
    Cc: tglx@linutronix.de; mingo@redhat.com; bp@alien8.de; bp@suse.de; x86@kernel.org; linux-kernel@vger.kernel.org; hpa@zytor.com
    Subject: Re: [PATCH] x86/nmi: Fix nmi_handle duration miscalculation

    On Mon, Aug 17, 2020 at 05:04:41PM +0800, Libing Zhou wrote:
    > In nmi_check_duration(), the 'whole_msecs' value should get from
    > 'duration' to reflect actual time duration, but not
    > 'action->max_duration'.

    Fixes: 248ed51048c4 ("x86/nmi: Remove irq_work from the long duration NMI handler")

    > Signed-off-by: Libing Zhou <libing.zhou@nokia-sbell.com>
    > ---
    > arch/x86/kernel/nmi.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index
    > 4fc9954a9560..c51ee659e520 100644
    > --- a/arch/x86/kernel/nmi.c
    > +++ b/arch/x86/kernel/nmi.c
    > @@ -102,7 +102,7 @@ fs_initcall(nmi_warning_debugfs);
    >
    > static void nmi_check_duration(struct nmiaction *action, u64
    > duration) {
    > - u64 whole_msecs = READ_ONCE(action->max_duration);
    > + u64 whole_msecs = duration;
    > int remainder_ns, decimal_msecs;
    >
    > if (duration < nmi_longest_ns || duration < action->max_duration)

    The, IMO, saner solution is:

    ---
    diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 4fc9954a9560..47381666d6a5 100644
    --- a/arch/x86/kernel/nmi.c
    +++ b/arch/x86/kernel/nmi.c
    @@ -102,7 +102,6 @@ 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) @@ -110,12 +109,12 @@ 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)
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