[PATCH 3/3] powernv: Fix MCE handler to avoid trashing CR0/CR1 registers.
Mahesh J Salgaonkar
mahesh at linux.vnet.ibm.com
Thu Feb 25 15:55:46 AEDT 2016
From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
The current implementation of MCE early handling modifies CR0/1 registers
without saving its old values. Fix this by moving early check for
powersaving mode to machine_check_handle_early().
The power architecture 2.06 or later allows the possibility of getting
machine check while in nap/sleep/winkle. The last bit of HSPRG0 is set
to 1, if thread is woken up from winkle. Hence, clear the last bit of
HSPRG0 (r13) before MCE handler starts using it as paca pointer.
Also, the current code always puts the thread into nap state irrespective
of whatever idle state it woke up from. Fix that by looking at
paca->thread_idle_state and put the thread back into same state where it
came from.
Reported-by: Paul Mackerras <paulus at samba.org>
Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
arch/powerpc/kernel/exceptions-64s.S | 66 ++++++++++++++++++++--------------
1 file changed, 39 insertions(+), 27 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index d4c99f0..7fa71e7 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -164,29 +164,14 @@ machine_check_pSeries_1:
* vector
*/
SET_SCRATCH0(r13) /* save r13 */
-#ifdef CONFIG_PPC_P7_NAP
-BEGIN_FTR_SECTION
- /* Running native on arch 2.06 or later, check if we are
- * waking up from nap. We only handle no state loss and
- * supervisor state loss. We do -not- handle hypervisor
- * state loss at this time.
+ /*
+ * Running native on arch 2.06 or later, we may wakeup from winkle
+ * inside machine check. If yes, then last bit of HSPGR0 would be set
+ * to 1. Hence clear it unconditionally.
*/
- mfspr r13,SPRN_SRR1
- rlwinm. r13,r13,47-31,30,31
- OPT_GET_SPR(r13, SPRN_CFAR, CPU_FTR_CFAR)
- beq 9f
-
- mfspr r13,SPRN_SRR1
- rlwinm. r13,r13,47-31,30,31
- /* waking up from powersave (nap) state */
- cmpwi cr1,r13,2
- /* Total loss of HV state is fatal. let's just stay stuck here */
- OPT_GET_SPR(r13, SPRN_CFAR, CPU_FTR_CFAR)
- bgt cr1,.
-9:
- OPT_SET_SPR(r13, SPRN_CFAR, CPU_FTR_CFAR)
-END_FTR_SECTION_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
-#endif /* CONFIG_PPC_P7_NAP */
+ GET_PACA(r13)
+ clrrdi r13,r13,1
+ SET_PACA(r13)
EXCEPTION_PROLOG_0(PACA_EXMC)
BEGIN_FTR_SECTION
b machine_check_powernv_early
@@ -1362,25 +1347,52 @@ machine_check_handle_early:
* Check if thread was in power saving mode. We come here when any
* of the following is true:
* a. thread wasn't in power saving mode
- * b. thread was in power saving mode with no state loss or
- * supervisor state loss
+ * b. thread was in power saving mode with no state loss,
+ * supervisor state loss or hypervisor state loss.
*
- * Go back to nap again if (b) is true.
+ * Go back to nap/sleep/winkle mode again if (b) is true.
*/
rlwinm. r11,r12,47-31,30,31 /* Was it in power saving mode? */
beq 4f /* No, it wasn;t */
/* Thread was in power saving mode. Go back to nap again. */
cmpwi r11,2
- bne 3f
- /* Supervisor state loss */
+ blt 3f
+ /* Supervisor/Hypervisor state loss loss */
li r0,1
stb r0,PACA_NAPSTATELOST(r13)
3: bl machine_check_queue_event
MACHINE_CHECK_HANDLER_WINDUP
GET_PACA(r13)
+ /*
+ * Check what idle state this CPU was in and go back to same mode
+ * again.
+ */
+ lbz r3,PACA_THREAD_IDLE_STATE(r13)
+ cmpwi r3,PNV_THREAD_NAP
+ bgt 1f
ld r1,PACAR1(r13)
li r3,PNV_THREAD_NAP
b power7_enter_nap_mode
+ /* No return */
+1:
+ cmpwi r3,PNV_THREAD_SLEEP
+ bgt 2f
+ IDLE_STATE_ENTER_SEQ(PPC_SLEEP)
+ /* No return */
+
+2:
+ /*
+ * Go back to winkle. Please note that this thread was woken up in
+ * machine check from winkle and have not restored the per-subcore
+ * state. Hence before going back to winkle, set last bit of HSPGR0
+ * to 1. This will make sure that if this thread gets woken up
+ * again at reset vector 0x100 then it will get chance to restore
+ * the subcore state.
+ */
+ ori r13,r13,1
+ SET_PACA(r13)
+ IDLE_STATE_ENTER_SEQ(PPC_WINKLE)
+ /* No return */
4:
#endif
/*
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