Re: [RFC PATCH 5/5] GHES: Make NMI handler have a single reader

Borislav Petkov
2015-04-28T07:38:38Z

On Tue, Apr 28, 2015 at 02:24:16AM +0000, Zheng, Lv wrote:
> > > #APP
> > > # 177 "./arch/x86/include/asm/atomic.h" 1
> > > .pushsection .smp_locks,"a"
> > > .balign 4
> > > .long 671f - .
> > > .popsection
> > > 671:
> > > lock; cmpxchgl %edx,ghes_in_nmi(%rip) # D.37056, MEM[(volatile u32 *)&ghes_in_nmi]
> > > # 0 "" 2
> > > #NO_APP
> > >
> > > And you need to atomic_dec() so that another reader can enter, i.e. how
> > > the exclusion primitive works.
> > >
> > > Or did you have something else in mind?
> >
> > My mistake.
> > I mean cmpxchg() and xchg() (or atomic_cmpxchg() and atomic_xchg()) pair here, so nothing can be reduced.
>
> Let me correct, it should be atomic_cmpxchg() and atomic_set() here as you only need to switch between 0 and 1.
> Sorry for the noise.

I still don't understand what you want from me here. You need to go into
more detail.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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