powerpc: Fix unpaired __trace_hcall_entry and __trace_hcall_exit

 Unpaired calling of __trace_hcall_entry and __trace_hcall_exit could
 cause incorrect preempt count. And it might happen as the global
 variable hcall_tracepoint_refcount is checked separately before calling
 them.

 Instead, store the value that was used on entry in the stack frame
 and retreive it from there after the call

Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S
index fd05fdee576a..3ce73d0052b1 100644
--- a/arch/powerpc/platforms/pseries/hvCall.S
+++ b/arch/powerpc/platforms/pseries/hvCall.S
@@ -36,6 +36,7 @@ BEGIN_FTR_SECTION;						\
         b       1f;                                             \
 END_FTR_SECTION(0, 1);                                          \
         ld      r12,hcall_tracepoint_refcount@toc(r2);          \
+        std     r12,32(r1);                                     \
         cmpdi   r12,0;                                          \
         beq+    1f;                                             \
         mflr    r0;                                             \
@@ -74,7 +75,7 @@ END_FTR_SECTION(0, 1);						\
 BEGIN_FTR_SECTION;                                              \
         b       1f;                                             \
 END_FTR_SECTION(0, 1);                                          \
-        ld      r12,hcall_tracepoint_refcount@toc(r2);          \
+        ld      r12,32(r1);                                     \
         cmpdi   r12,0;                                          \
         beq+    1f;                                             \
         mflr    r0;                                             \