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Commit c2d52644 authored Aug 09, 2013 by Michael Neuling Committed by Benjamin Herrenschmidt Aug 09, 2013

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>

parent 2517617e

arch/powerpc/include/asm/switch_to.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -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);

arch/powerpc/kernel/entry_64.S

+0 −9

Original line number	Diff line number	Diff line
		@@ -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)

arch/powerpc/kernel/process.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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