linux-kernel - Re: [PATCH] powerpc/traps: restore recoverability of machine

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Date:   Tue, 16 Oct 2018 11:10:04 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Christophe LEROY <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] powerpc/traps: restore recoverability of machine_check
 interrupts

On Mon, 15 Oct 2018 09:40:50 +0200
Christophe LEROY <christophe.leroy@....fr> wrote:

> Cc: stable@...r.kernel.org <stable@...r.kernel.org>
> 
> Le 13/10/2018 à 11:16, Christophe Leroy a écrit :
> > commit b96672dd840f ("powerpc: Machine check interrupt is a non-
> > maskable interrupt") added a call to nmi_enter() at the beginning of
> > machine check restart exception handler. Due to that, in_interrupt()
> > always returns true regardless of the state before entering the
> > exception, and die() panics even when the system was not already in
> > interrupt.
> > 
> > This patch calls nmi_exit() before calling die() in order to restore
> > the interrupt state we had before calling nmi_enter()
> > 
> > Fixes: b96672dd840f ("powerpc: Machine check interrupt is a non-maskable interrupt")
> > Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

This looks good to me and probably the simplest fix.

powernv will need a fix on top of this, to remove the die and let it
just fall through unrecovered to the traps.c code. pseries seems to
be okay. But this patch looks good.

Thanks,
Nick