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powerpc: Save the TAR register earlier 

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>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Neuling 2013-08-09 17:29:30 +10:00 committed by Benjamin Herrenschmidt
parent 2517617e0d
commit c2d52644e2
3 changed files with 19 additions and 9 deletions
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9
arch/powerpc/include/asm/switch_to.h
View File

@ -15,6 +15,15 @@ extern struct task_struct *__switch_to(struct task_struct *,
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);

9
arch/powerpc/kernel/entry_64.S
View File

@ -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)

10
arch/powerpc/kernel/process.c
View File

@ -600,6 +600,16 @@ struct task_struct *__switch_to(struct task_struct *prev,
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