linux-kernel - [PATCH AUTOSEL 4.14 05/30] powerpc/traps: restore recoverability of machine

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Date:   Sun,  4 Nov 2018 08:53:00 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Christophe Leroy <christophe.leroy@....fr>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 05/30] powerpc/traps: restore recoverability of machine_check interrupts

From: Christophe Leroy <christophe.leroy@....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@....fr>
Reviewed-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 ac2e5e56a9f0..a5f2b7593976 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -694,12 +694,17 @@ 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();
-- 
2.17.1