This is a note to let you know that I've just added the patch titled
powerpc/powernv: Switch off MMU before entering nap/sleep/rvwinkle mode
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-powernv-switch-off-mmu-before-entering-nap-sleep-rvwinkle-mode.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8117ac6a6c2fa0f847ff6a21a1f32c8d2c8501d0 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxx>
Date: Wed, 10 Dec 2014 00:26:50 +0530
Subject: powerpc/powernv: Switch off MMU before entering nap/sleep/rvwinkle mode
From: Paul Mackerras <paulus@xxxxxxxxx>
commit 8117ac6a6c2fa0f847ff6a21a1f32c8d2c8501d0 upstream.
Currently, when going idle, we set the flag indicating that we are in
nap mode (paca->kvm_hstate.hwthread_state) and then execute the nap
(or sleep or rvwinkle) instruction, all with the MMU on. This is bad
for two reasons: (a) the architecture specifies that those instructions
must be executed with the MMU off, and in fact with only the SF, HV, ME
and possibly RI bits set, and (b) this introduces a race, because as
soon as we set the flag, another thread can switch the MMU to a guest
context. If the race is lost, this thread will typically start looping
on relocation-on ISIs at 0xc...4400.
This fixes it by setting the MSR as required by the architecture before
setting the flag or executing the nap/sleep/rvwinkle instruction.
[ shreyas@xxxxxxxxxxxxxxxxxx: Edited to handle LE ]
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Shreyas B. Prabhu <shreyas@xxxxxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/reg.h | 2 ++
arch/powerpc/kernel/idle_power7.S | 18 +++++++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -118,8 +118,10 @@
#define __MSR (MSR_ME | MSR_RI | MSR_IR | MSR_DR | MSR_ISF |MSR_HV)
#ifdef __BIG_ENDIAN__
#define MSR_ __MSR
+#define MSR_IDLE (MSR_ME | MSR_SF | MSR_HV)
#else
#define MSR_ (__MSR | MSR_LE)
+#define MSR_IDLE (MSR_ME | MSR_SF | MSR_HV | MSR_LE)
#endif
#define MSR_KERNEL (MSR_ | MSR_64BIT)
#define MSR_USER32 (MSR_ | MSR_PR | MSR_EE)
--- a/arch/powerpc/kernel/idle_power7.S
+++ b/arch/powerpc/kernel/idle_power7.S
@@ -101,7 +101,23 @@ _GLOBAL(power7_powersave_common)
std r9,_MSR(r1)
std r1,PACAR1(r13)
-_GLOBAL(power7_enter_nap_mode)
+ /*
+ * Go to real mode to do the nap, as required by the architecture.
+ * Also, we need to be in real mode before setting hwthread_state,
+ * because as soon as we do that, another thread can switch
+ * the MMU context to the guest.
+ */
+ LOAD_REG_IMMEDIATE(r5, MSR_IDLE)
+ li r6, MSR_RI
+ andc r6, r9, r6
+ LOAD_REG_ADDR(r7, power7_enter_nap_mode)
+ mtmsrd r6, 1 /* clear RI before setting SRR0/1 */
+ mtspr SPRN_SRR0, r7
+ mtspr SPRN_SRR1, r5
+ rfid
+
+ .globl power7_enter_nap_mode
+power7_enter_nap_mode:
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
/* Tell KVM we're napping */
li r4,KVM_HWTHREAD_IN_NAP
Patches currently in stable-queue which might be from paulus@xxxxxxxxx are
queue-3.18/powerpc-powernv-switch-off-mmu-before-entering-nap-sleep-rvwinkle-mode.patch
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