From 4d0d7c02df680740da41f5f92a238c35796ca5be Mon Sep 17 00:00:00 2001
From: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Date: Wed, 28 Jun 2017 06:46:49 +0530
Subject: [PATCH] powerpc/powernv/idle: Clear r12 on wakeup from stop lite
References: bsc#1055121
Patch-mainline: v4.13-rc1
Git-commit: 4d0d7c02df680740da41f5f92a238c35796ca5be
pnv_wakeup_noloss() expects r12 to contain SRR1 value to determine if the wakeup
reason is an HMI in CHECK_HMI_INTERRUPT.
When we wakeup with ESL=0, SRR1 will not contain the wakeup reason, so there is
no point setting r12 to SRR1.
However, we don't set r12 at all so r12 contains garbage (likely a kernel
pointer), and is still used to check HMI assuming that it contained SRR1. This
causes the OPAL msglog to be filled with the following print:
HMI: Received HMI interrupt: HMER = 0x0040000000000000
This patch clears r12 after waking up from stop with ESL=EC=0, so that we don't
accidentally enter the HMI handler in pnv_wakeup_noloss() if the value of
r12[42:45] corresponds to HMI as wakeup reason.
Prior to commit 9d29250136f6 ("powerpc/64s/idle: Avoid SRR usage in idle
sleep/wake paths") this bug existed, in that we would incorrectly look at SRR1
to check for a HMI when SRR1 didn't contain a wakeup reason. However the SRR1
value would just happen to never have bits 42:45 set.
Fixes: 9d29250136f6 ("powerpc/64s/idle: Avoid SRR usage in idle sleep/wake paths")
Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Change log and comment massaging]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/idle_book3s.S | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index f6518c768d2a..5adb390e773b 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -256,6 +256,19 @@ power_enter_stop:
bne .Lhandle_esl_ec_set
IDLE_STATE_ENTER_SEQ(PPC_STOP)
li r3,0 /* Since we didn't lose state, return 0 */
+
+ /*
+ * pnv_wakeup_noloss() expects r12 to contain the SRR1 value so
+ * it can determine if the wakeup reason is an HMI in
+ * CHECK_HMI_INTERRUPT.
+ *
+ * However, when we wakeup with ESL=0, SRR1 will not contain the wakeup
+ * reason, so there is no point setting r12 to SRR1.
+ *
+ * Further, we clear r12 here, so that we don't accidentally enter the
+ * HMI in pnv_wakeup_noloss() if the value of r12[42:45] == WAKE_HMI.
+ */
+ li r12, 0
b pnv_wakeup_noloss
.Lhandle_esl_ec_set:
--
2.13.6