[PATCH 4.18 001/171] powerpc/traps: restore recoverability of machine_check interrupts

Greg Kroah-Hartman
2018-11-19T16:39:38Z

From: Christophe Leroy <christophe.leroy@c-s.fr>

[ Upstream commit daf00ae71dad8aa05965713c62558aeebf2df48e ]

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/traps.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -736,12 +736,17 @@ void machine_check_exception(struct pt_r
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();