[PATCH] powerpc/traps: restore recoverability of machine_check interrupts

[PATCH] powerpc/traps: restore recoverability of machine_check interrupts

[Christophe Leroy]

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@c-s.fr>
---
 arch/powerpc/kernel/traps.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index fd58749b4d6b..4f880c2a6e4c 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -765,12 +765,17 @@ void machine_check_exception(struct pt_regs *regs)
 	if (check_io_access(regs))
 		goto bail;
 
-	die("Machine check", regs, SIGBUS);
-
 	/* Must die if the interrupt is not recoverable */
 	if (!(regs->msr & MSR_RI))
 		nmi_panic(regs, "Unrecoverable Machine check");
 
+	if (!nested)
+		nmi_exit();
+
+	die("Machine check", regs, SIGBUS);
+
+	return;
+
 bail:
 	if (!nested)
 		nmi_exit();
-- 
2.13.3

Re: [PATCH] powerpc/traps: restore recoverability of machine_check interrupts

[Christophe LEROY]

Cc: stable@vger.kernel.org <stable@vger.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@c-s.fr>
> ---
>   arch/powerpc/kernel/traps.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index fd58749b4d6b..4f880c2a6e4c 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -765,12 +765,17 @@ void machine_check_exception(struct pt_regs *regs)
>   	if (check_io_access(regs))
>   		goto bail;
>   
> -	die("Machine check", regs, SIGBUS);
> -
>   	/* Must die if the interrupt is not recoverable */
>   	if (!(regs->msr & MSR_RI))
>   		nmi_panic(regs, "Unrecoverable Machine check");
>   
> +	if (!nested)
> +		nmi_exit();
> +
> +	die("Machine check", regs, SIGBUS);
> +
> +	return;
> +
>   bail:
>   	if (!nested)
>   		nmi_exit();
> 

Re: [PATCH] powerpc/traps: restore recoverability of machine_check interrupts

[Nicholas Piggin]

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

> Cc: stable@vger.kernel.org <stable@vger.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@c-s.fr>

Reviewed-by: Nicholas Piggin <npiggin@gmail.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

Re: powerpc/traps: restore recoverability of machine_check interrupts

[Michael Ellerman]

On Sat, 2018-10-13 at 09:16:22 UTC, Christophe Leroy wrote:
> 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@c-s.fr>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/daf00ae71dad8aa05965713c62558a

cheers