linux-kernel - [PATCH v2 21/35] powerpc/64s/exception: soft nmi interrupt should not use ret_from

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Date:   Tue, 26 Nov 2019 21:13:35 +0100
From:   Michal Suchanek <msuchanek@...e.de>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Oleg Nesterov <oleg@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        Nicholas Piggin <npiggin@...il.com>,
        Allison Randal <allison@...utok.net>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Michal Suchanek <msuchanek@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Breno Leitao <leitao@...ian.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        Russell Currey <ruscur@...sell.cc>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Firoz Khan <firoz.khan@...aro.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Nicolai Stange <nstange@...e.de>,
        Valentin Schneider <valentin.schneider@....com>,
        Diana Craciun <diana.craciun@....com>,
        Daniel Axtens <dja@...ens.net>,
        Michael Neuling <mikey@...ling.org>,
        Gustavo Romero <gromero@...ux.ibm.com>,
        Mathieu Malaterre <malat@...ian.org>,
        "Steven Rostedt" <rostedt@...dmis.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        David Howells <dhowells@...hat.com>,
        Brajeswar Ghosh <brajeswar.linux@...il.com>,
        Jagadeesh Pagadala <jagdsh.linux@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 21/35] powerpc/64s/exception: soft nmi interrupt should not use ret_from_except

From: Nicholas Piggin <npiggin@...il.com>

The soft nmi handler does not reconcile interrupt state, so it should
not return via the normal ret_from_except path. Return like other NMIs,
using the EXCEPTION_RESTORE_REGS macro.

This becomes important when the scv interrupt is implemented, which
must handle soft-masked interrupts that have r13 set to something other
than the PACA -- returning to kernel in this case must restore r13.

Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
 arch/powerpc/kernel/exceptions-64s.S | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 38bc66b95516..af1264cd005f 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2740,7 +2740,11 @@ EXC_COMMON_BEGIN(soft_nmi_common)
 	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	soft_nmi_interrupt
-	b	ret_from_except
+	/* Clear MSR_RI before setting SRR0 and SRR1. */
+	li	r9,0
+	mtmsrd	r9,1
+	EXCEPTION_RESTORE_REGS hsrr=0
+	RFI_TO_KERNEL
 
 #endif /* CONFIG_PPC_WATCHDOG */
 
-- 
2.23.0