Re: [PATCH -v2 7/7] x86, NMI, Remove do_nmi_callback logic

Robert Richter
2010-09-27T16:59:39Z

On 27.09.10 11:16:07, Don Zickus wrote:
> On Mon, Sep 27, 2010 at 03:43:41PM +0200, Robert Richter wrote:
> > On 27.09.10 08:56:44, huang ying wrote:
> >
> > > >> -static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
> > > >> -{
> > > >> -     unsigned char reason = get_nmi_reason();
> > > >> -     char buf[64];
> > > >> -
> > > >> -     sprintf(buf, "NMI received for unknown reason %02x\n", reason);
> > > >> -     die_nmi(buf, regs, 1); /* Always panic here */
> > > >> -     return 0;
> > > >
> > > > You are dropping this code that is different to panic().
> > >
> > > What is the difference? Is it relevant?
> >
> > I think yes, since the code behaves different. Otherwise we could
> > remove die_nmi() completly and replace it by panic(). But both are
> > different implementions. Maybe we can merge the code, but I didn't
> > look at it closly.
>
> Actually die_nmi is a wrapper around panic with two important pieces.
> One, it dumps some registers and two it does another notifier call to
> DIE_NMIWATCHDOG (which correlates to another discussion in this patch
> series).
>
> So if we do any consolidation between panic and die_nmi, it should be
> convert to die_nmi. But then I wonder if that breaks the original
> semantics of 'panic_on_unrecovered_nmi'. I don't think so though.

I agree, panic_on_unrecovered_nmi and unknown_nmi_panic almost do the
same thing, though die_nmi() is specifically for nmi handlers. In the
end we can consolidate both. We should then modify kernel.txt and
route unknown_nmi_panic to panic_on_unrecovered_nmi or vice versa.

-Robert

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Advanced Micro Devices, Inc.
Operating System Research Center