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Date:   Mon, 9 Nov 2015 09:09:06 +0100
From:   Ralf Baechle <ralf@linux-mips.org>
To:     Petri Gynther <pgynther@google.com>
Cc:     linux-mips <linux-mips@linux-mips.org>
Subject: Re: [PATCH] MIPS: add nmi_enter() + nmi_exit() to
 nmi_exception_handler()
Message-ID: <20151109080906.GA27251@linux-mips.org>
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On Mon, Nov 02, 2015 at 12:50:50PM -0800, Petri Gynther wrote:

> On Mon, Oct 19, 2015 at 11:49 AM, Petri Gynther <pgynther@google.com> wrote:
> >
> > We need to enter NMI context when NMI interrupt fires.
> >
> > Signed-off-by: Petri Gynther <pgynther@google.com>
> > ---
> >  arch/mips/kernel/traps.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> > index fdb392b..efcedd4 100644
> > --- a/arch/mips/kernel/traps.c
> > +++ b/arch/mips/kernel/traps.c
> > @@ -1856,12 +1856,14 @@ void __noreturn nmi_exception_handler(struct pt_regs *regs)
> >  {
> >         char str[100];
> >
> > +       nmi_enter();
> >         raw_notifier_call_chain(&nmi_chain, 0, regs);
> >         bust_spinlocks(1);
> >         snprintf(str, 100, "CPU%d NMI taken, CP0_EPC=%lx\n",
> >                  smp_processor_id(), regs->cp0_epc);
> >         regs->cp0_epc = read_c0_errorepc();
> >         die(str, regs);
> > +       nmi_exit();
> >  }
> >
> >  #define VECTORSPACING 0x100    /* for EI/VI mode */
> > --
> > 2.6.0.rc2.230.g3dd15c0
> >
> 
> Any comments/concerns about this patch?

Is NMI on your systems actually recoverable?  I never bothered with
nmi_enther / nmi_exit and other fine details of the NMI implementations
because as defined by the MIPS architecture an NMI may be pretty destructive
and closer to a reset than what other architectures describer as their NMI.
Think what's going to happen if it hits during any phase when $k0 / $k1
are active.

  Ralf