[PATCH] powerpc/book3s: Fix CFAR clobbering issue in machine check handler.

[Mahesh J Salgaonkar]

From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>

While checking powersaving mode in machine check handler at 0x200, we
clobber CFAR register. Fix it by saving and restoring it during beq/bgt.

Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/exception-64s.h |    8 ++++++++
 arch/powerpc/kernel/exceptions-64s.S     |    5 +++++
 2 files changed, 13 insertions(+)

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 6683061..aeaa56c 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -147,6 +147,14 @@ BEGIN_FTR_SECTION_NESTED(943)						\
 END_FTR_SECTION_NESTED(ftr,ftr,943)
 
 /*
+ * Set an SPR from a register if the CPU has the given feature
+ */
+#define OPT_SET_SPR(ra, spr, ftr)					\
+BEGIN_FTR_SECTION_NESTED(943)						\
+	mtspr	spr,ra;							\
+END_FTR_SECTION_NESTED(ftr,ftr,943)
+
+/*
  * Save a register to the PACA if the CPU has the given feature
  */
 #define OPT_SAVE_REG_TO_PACA(offset, ra, ftr)				\
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 38d5073..4c34c3c 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -164,13 +164,18 @@ BEGIN_FTR_SECTION
 	 */
 	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 */
 	EXCEPTION_PROLOG_0(PACA_EXMC)