[ 08/60] powerpc: Save the TAR register earlier

Greg Kroah-Hartman
2013-08-13T06:48:24Z

From: Michael Neuling <mikey@neuling.org>

commit c2d52644e2da8a07ecab5ca62dd0bc563089e8dc upstream.

This moves us to save the Target Address Register (TAR) a earlier in
__switch_to. It introduces a new function save_tar() to do this.

We need to save the TAR earlier as we will overwrite it in the transactional
memory reclaim/recheckpoint path. We are going to do this in a subsequent
patch which will fix saving the TAR register when it's modified inside a
transaction.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/include/asm/switch_to.h | 9 +++++++++
arch/powerpc/kernel/entry_64.S | 9 ---------
arch/powerpc/kernel/process.c | 10 ++++++++++
3 files changed, 19 insertions(+), 9 deletions(-)

--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -15,6 +15,15 @@ extern struct task_struct *__switch_to(s
struct thread_struct;
extern struct task_struct *_switch(struct thread_struct *prev,
struct thread_struct *next);
+#ifdef CONFIG_PPC_BOOK3S_64
+static inline void save_tar(struct thread_struct *prev)
+{
+ if (cpu_has_feature(CPU_FTR_ARCH_207S))
+ prev->tar = mfspr(SPRN_TAR);
+}
+#else
+static inline void save_tar(struct thread_struct *prev) {}
+#endif

extern void giveup_fpu(struct task_struct *);
extern void load_up_fpu(void);
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -449,15 +449,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_DSCR)

#ifdef CONFIG_PPC_BOOK3S_64
BEGIN_FTR_SECTION
- /*
- * Back up the TAR across context switches. Note that the TAR is not
- * available for use in the kernel. (To provide this, the TAR should
- * be backed up/restored on exception entry/exit instead, and be in
- * pt_regs. FIXME, this should be in pt_regs anyway (for debug).)
- */
- mfspr r0,SPRN_TAR
- std r0,THREAD_TAR(r3)
-
/* Event based branch registers */
mfspr r0, SPRN_BESCR
std r0, THREAD_BESCR(r3)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -600,6 +600,16 @@ struct task_struct *__switch_to(struct t
struct ppc64_tlb_batch *batch;
#endif

+ /* Back up the TAR across context switches.
+ * Note that the TAR is not available for use in the kernel. (To
+ * provide this, the TAR should be backed up/restored on exception
+ * entry/exit instead, and be in pt_regs. FIXME, this should be in
+ * pt_regs anyway (for debug).)
+ * Save the TAR here before we do treclaim/trecheckpoint as these
+ * will change the TAR.
+ */
+ save_tar(&prev->thread);
+
__switch_to_tm(prev);

#ifdef CONFIG_SMP