[PATCH] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[PATCH] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Commit 09206b600c76 ("powernv: Pass PSSCR value and mask to
power9_idle_stop") added additional code in power_enter_stop() to
distinguish between stop requests whose PSSCR had ESL=EC=1 from those
which did not. When ESL=EC=1, we do a forward-jump to a location
labelled by "1", which had the code to handle the ESL=EC=1 case.

Unforunately just a couple of instructions before this label, is the
macro IDLE_STATE_ENTER_SEQ() which also has a label "1" in its
expansion.

As a result, the current code can result in directly executing stop
instruction for deep stop requests with PSSCR ESL=EC=1, without saving
the hypervisor state.

Fix this BUG by labeling the location that handles ESL=EC=1 case with
a more descriptive label.

For a good measure, change the label in IDLE_STATE_ENTER_SEQ() macro
to an not-so commonly used value.

Fixes: 09206b600c76 ("powernv: Pass PSSCR value and mask to
power9_idle_stop")

Cc: Michael Neuling <mikey@neuling.org>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/cpuidle.h | 4 ++--
 arch/powerpc/kernel/idle_book3s.S  | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
index 31192d8..3989d94 100644
--- a/arch/powerpc/include/asm/cpuidle.h
+++ b/arch/powerpc/include/asm/cpuidle.h
@@ -85,8 +85,8 @@ static inline void report_invalid_psscr_val(u64 psscr_val, int err)
 	std	r0,0(r1);					\
 	ptesync;						\
 	ld	r0,0(r1);					\
-1:	cmpd	cr0,r0,r0;					\
-	bne	1b;						\
+236:	cmpd	cr0,r0,r0;					\
+	bne	236b;						\
 	IDLE_INST;						\
 
 #define	IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST)			\
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 9f6bce5..95889af 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -276,14 +276,16 @@ power_enter_stop:
  */
 	andis.   r4,r3,PSSCR_EC_ESL_MASK_SHIFTED
 	clrldi   r3,r3,60 /* r3 = Bits[60:63] = Requested Level (RL) */
-	bne	 1f
+	bne	 handle_esl_ec_set
 	IDLE_STATE_ENTER_SEQ(PPC_STOP)
 	li	r3,0  /* Since we didn't lose state, return 0 */
 	b 	pnv_wakeup_noloss
+
+handle_esl_ec_set:
 /*
  * Check if the requested state is a deep idle state.
  */
-1:	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
+	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
 	ld	r4,ADDROFF(pnv_first_deep_stop_state)(r5)
 	cmpd	r3,r4
 	bge	2f
-- 
1.8.3.1

Re: [PATCH] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[Anton Blanchard]

Hi Gautham,

> +handle_esl_ec_set:

Unless we want to expose this to things like perf, we might want to
make it a local label (eg .Lxx)

Anton

Re: [PATCH] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[Gautham R Shenoy]

Hi Anton,
On Mon, Feb 27, 2017 at 10:37:07AM +1100, Anton Blanchard wrote:
> Hi Gautham,
> 
> > +handle_esl_ec_set:
> 
> Unless we want to expose this to things like perf, we might want to
> make it a local label (eg .Lxx)

Sure. We don't want to expose this to perf at least as of now! Will
resend the patch with a local label.
> 
> Anton
>

--
Thanks and Regards
gautham.

[v2 PATCH] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Commit 09206b600c76 ("powernv: Pass PSSCR value and mask to
power9_idle_stop") added additional code in power_enter_stop() to
distinguish between stop requests whose PSSCR had ESL=EC=1 from those
which did not. When ESL=EC=1, we do a forward-jump to a location
labelled by "1", which had the code to handle the ESL=EC=1 case.

Unforunately just a couple of instructions before this label, is the
macro IDLE_STATE_ENTER_SEQ() which also has a label "1" in its
expansion.

As a result, the current code can result in directly executing stop
instruction for deep stop requests with PSSCR ESL=EC=1, without saving
the hypervisor state.

Fix this BUG by labeling the location that handles ESL=EC=1 case with
a more descriptive label ".Lhandle_esl_ec_set" (local label suggestion
a la .Lxx from Anton Blanchard).

While at it, rename the label "2" labelling the location of the code
handling entry into deep stop states with ".Lhandle_deep_stop".

For a good measure, change the label in IDLE_STATE_ENTER_SEQ() macro
to an not-so commonly used value in order to avoid similar mishaps in
the future.

Fixes: 09206b600c76 ("powernv: Pass PSSCR value and mask to
power9_idle_stop")

Cc: Michael Neuling <mikey@neuling.org>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
Changes from v1: 
  a) Use local label style for the updated descriptive label names.
  b) Add descriptive label to code handling entry into deep stop states.

 arch/powerpc/include/asm/cpuidle.h |  4 ++--
 arch/powerpc/kernel/idle_book3s.S  | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
index 31192d8..3989d94 100644
--- a/arch/powerpc/include/asm/cpuidle.h
+++ b/arch/powerpc/include/asm/cpuidle.h
@@ -85,8 +85,8 @@ static inline void report_invalid_psscr_val(u64 psscr_val, int err)
 	std	r0,0(r1);					\
 	ptesync;						\
 	ld	r0,0(r1);					\
-1:	cmpd	cr0,r0,r0;					\
-	bne	1b;						\
+236:	cmpd	cr0,r0,r0;					\
+	bne	236b;						\
 	IDLE_INST;						\
 
 #define	IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST)			\
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 9f6bce5..28fcb39 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -276,19 +276,21 @@ power_enter_stop:
  */
 	andis.   r4,r3,PSSCR_EC_ESL_MASK_SHIFTED
 	clrldi   r3,r3,60 /* r3 = Bits[60:63] = Requested Level (RL) */
-	bne	 1f
+	bne	 .Lhandle_esl_ec_set
 	IDLE_STATE_ENTER_SEQ(PPC_STOP)
 	li	r3,0  /* Since we didn't lose state, return 0 */
 	b 	pnv_wakeup_noloss
+
+.Lhandle_esl_ec_set:
 /*
  * Check if the requested state is a deep idle state.
  */
-1:	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
+	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
 	ld	r4,ADDROFF(pnv_first_deep_stop_state)(r5)
 	cmpd	r3,r4
-	bge	2f
+	bge	.Lhandle_deep_stop
 	IDLE_STATE_ENTER_SEQ_NORET(PPC_STOP)
-2:
+.Lhandle_deep_stop:
 /*
  * Entering deep idle state.
  * Clear thread bit in PACA_CORE_IDLE_STATE, save SPRs to
-- 
1.9.4

Re: [v2] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

[Michael Ellerman]

On Mon, 2017-02-27 at 05:40:07 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> Commit 09206b600c76 ("powernv: Pass PSSCR value and mask to
> power9_idle_stop") added additional code in power_enter_stop() to
> distinguish between stop requests whose PSSCR had ESL=EC=1 from those
> which did not. When ESL=EC=1, we do a forward-jump to a location
> labelled by "1", which had the code to handle the ESL=EC=1 case.
> 
> Unforunately just a couple of instructions before this label, is the
> macro IDLE_STATE_ENTER_SEQ() which also has a label "1" in its
> expansion.
> 
> As a result, the current code can result in directly executing stop
> instruction for deep stop requests with PSSCR ESL=EC=1, without saving
> the hypervisor state.
> 
> Fix this BUG by labeling the location that handles ESL=EC=1 case with
> a more descriptive label ".Lhandle_esl_ec_set" (local label suggestion
> a la .Lxx from Anton Blanchard).
> 
> While at it, rename the label "2" labelling the location of the code
> handling entry into deep stop states with ".Lhandle_deep_stop".
> 
> For a good measure, change the label in IDLE_STATE_ENTER_SEQ() macro
> to an not-so commonly used value in order to avoid similar mishaps in
> the future.
> 
> Fixes: 09206b600c76 ("powernv: Pass PSSCR value and mask to
> power9_idle_stop")
> 
> Cc: Michael Neuling <mikey@neuling.org>
> Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/424f8acd328a111319ae30bf384e5d

cheers