This is a note to let you know that I've just added the patch titled x86/nmi: Fix nmi_handle() duration miscalculation to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-nmi-fix-nmi_handle-duration-miscalculation.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d2b0d86e6213bf791d2948930bef918da14fde4e Author: Libing Zhou <libing.zhou@xxxxxxxxxxxxxxx> Date: Thu Aug 20 10:56:41 2020 +0800 x86/nmi: Fix nmi_handle() duration miscalculation [ 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@xxxxxxxxxxxxx> Signed-off-by: Libing Zhou <libing.zhou@xxxxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Changbin Du <changbin.du@xxxxxxxxx> Link: https://lkml.kernel.org/r/20200820025641.44075-1-libing.zhou@xxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 4fc9954a95600..47381666d6a55 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)