x86/nmi: Fix nmi_handle() duration miscalculation

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

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 4fc9954a956003d42f3c6e4fc3847f7d1f837f30..47381666d6a55b27173ff611dd1d5642338ed47f 100644 (file)
--- 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)