RE: [PATCH v11 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH_STOP should try for NMI

[Tomohiro Misono (Fujitsu)]

> -----Original Message----- 
> There's no reason why IPI_CPU_STOP and IPI_CPU_CRASH_STOP can't be
> handled as NMI. They are very simple and everything in them is
> NMI-safe. Mark them as things to use NMI for if NMI is available.
> 
> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
> Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> ---
> I don't actually have any good way to test/validate this patch. It's
> added to the series at Mark's request.

For IPI_CPU_CRASH_STOP, I briefly checked that HARDLOCKUP-ed CPU
(by lkdtm) received the ipi upon crash dump request when pseudo NMI is
enabled.
  Reviewed-by: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxx>

Regards,
Tomohiro

> 
> (no changes since v10)
> 
> Changes in v10:
> - ("IPI_CPU_STOP and IPI_CPU_CRASH_STOP should try for NMI") new for
> v10.
> 
>  arch/arm64/kernel/smp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index c8896cbc5327..4566934aaf9f 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -946,6 +946,8 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi)
>  		return false;
> 
>  	switch (ipi) {
> +	case IPI_CPU_STOP:
> +	case IPI_CPU_CRASH_STOP:
>  	case IPI_CPU_BACKTRACE:
>  		return true;
>  	default:
> --
> 2.42.0.rc1.204.g551eb34607-goog
> 
> 
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