diff mbox

[v2,1/2] Powernv: Remove the usage of PACAR1 from opal wrappers

Message ID 20160515041413.2280.747.stgit@mars
State Accepted
Headers show

Commit Message

Mahesh J Salgaonkar May 15, 2016, 4:14 a.m. UTC 
From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

OPAL_CALL wrapper code sticks the r1 (stack pointer) into PACAR1 purely
for debugging purpose only. The power7_wakeup* functions relies on stack
pointer saved in PACAR1. Any opal call made using opal wrapper (directly
or in-directly) before we fall through power7_wakeup*, then it ends up
replacing r1 in PACAR1(r13) leading to kernel panic. So far we don't see
any issues because we have never made any opal calls using OPAL wrapper
before power7_wakeup*. But the subsequent HMI patch would need to invoke
C calls during cpu wakeup/idle path that in-directly makes opal call using
opal wrapper. This patch facilitates the subsequent HMI patch by removing
usage of PACAR1 from opal call wrapper.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/platforms/powernv/opal-wrappers.S |    2 --
 1 file changed, 2 deletions(-)


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Comments

Paul Mackerras June 24, 2016, 9:21 a.m. UTC | #1 
On Sun, May 15, 2016 at 09:44:13AM +0530, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> OPAL_CALL wrapper code sticks the r1 (stack pointer) into PACAR1 purely
> for debugging purpose only. The power7_wakeup* functions relies on stack
> pointer saved in PACAR1. Any opal call made using opal wrapper (directly
> or in-directly) before we fall through power7_wakeup*, then it ends up
> replacing r1 in PACAR1(r13) leading to kernel panic. So far we don't see
> any issues because we have never made any opal calls using OPAL wrapper
> before power7_wakeup*. But the subsequent HMI patch would need to invoke
> C calls during cpu wakeup/idle path that in-directly makes opal call using
> opal wrapper. This patch facilitates the subsequent HMI patch by removing
> usage of PACAR1 from opal call wrapper.
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au>

Thanks, both patches applied to my kvm-ppc-next branch at
git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc.git.

Paul.
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diff mbox

Patch

diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index e45b88a..df6ad94 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -64,7 +64,6 @@  END_FTR_SECTION(0, 1);						\
 	OPAL_BRANCH(opal_tracepoint_entry) \
 	mfcr	r12;			\
 	stw	r12,8(r1);		\
-	std	r1,PACAR1(r13);		\
 	li	r11,0;			\
 	mfmsr	r12;			\
 	ori	r11,r11,MSR_EE;		\
@@ -127,7 +126,6 @@  opal_tracepoint_entry:
 	mfcr	r12
 	std	r11,16(r1)
 	stw	r12,8(r1)
-	std	r1,PACAR1(r13)
 	li	r11,0
 	mfmsr	r12
 	ori	r11,r11,MSR_EE