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From:   Julien Thierry <julien.thierry@arm.com>
To:     linux-arm-kernel@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, daniel.thompson@linaro.org,
        joel@joelfernandes.org, marc.zyngier@arm.com,
        christoffer.dall@arm.com, james.morse@arm.com,
        catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com,
        Julien Thierry <julien.thierry@arm.com>,
        Dave Martin <dave.martin@arm.com>
Subject: [PATCH v10 22/25] arm64: Handle serror in NMI context
Date:   Thu, 31 Jan 2019 14:59:00 +0000
Message-Id: <1548946743-38979-23-git-send-email-julien.thierry@arm.com>
In-Reply-To: <1548946743-38979-1-git-send-email-julien.thierry@arm.com>
References: <1548946743-38979-1-git-send-email-julien.thierry@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
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Per definition of the daifflags, Serrors can occur during any interrupt
context, that includes NMI contexts. Trying to nmi_enter in an nmi context
will crash.

Skip nmi_enter/nmi_exit when serror occurred during an NMI.

Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/traps.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 4e2fb87..8ad119c 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -898,13 +898,17 @@ bool arm64_is_fatal_ras_serror(struct pt_regs *regs, unsigned int esr)
 
 asmlinkage void do_serror(struct pt_regs *regs, unsigned int esr)
 {
-	nmi_enter();
+	const bool was_in_nmi = in_nmi();
+
+	if (!was_in_nmi)
+		nmi_enter();
 
 	/* non-RAS errors are not containable */
 	if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(regs, esr))
 		arm64_serror_panic(regs, esr);
 
-	nmi_exit();
+	if (!was_in_nmi)
+		nmi_exit();
 }
 
 void __pte_error(const char *file, int line, unsigned long val)
-- 
1.9.1