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Commit 0df977ea authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS 



When calling RTAS, the stack pointer is stored in SPRN_SPRG2
in order to be able to restore it in case of machine check in RTAS.

As machine check is not a perfomance critical path, this patch
frees SPRN_SPRG2 by using a field in thread struct instead.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 40058337

arch/powerpc/include/asm/processor.h

+3 −0
Original line number Diff line number Diff line
@@ -250,6 +250,9 @@ struct thread_struct { 
#ifdef CONFIG_PPC32

	void		*pgdir;		/* root of page-table tree */

	unsigned long	ksp_limit;	/* if ksp <= ksp_limit stack overflow */

#ifdef CONFIG_PPC_RTAS

	unsigned long	rtas_sp;	/* stack pointer for when in RTAS */

#endif

#endif

	/* Debug Registers */

	struct debug_reg debug;

arch/powerpc/include/asm/reg.h

+0 −1
Original line number Diff line number Diff line
@@ -1167,7 +1167,6 @@ 
#ifdef CONFIG_PPC_BOOK3S_32

#define SPRN_SPRG_SCRATCH0	SPRN_SPRG0

#define SPRN_SPRG_SCRATCH1	SPRN_SPRG1

#define SPRN_SPRG_RTAS		SPRN_SPRG2

#define SPRN_SPRG_603_LRU	SPRN_SPRG4

#endif

arch/powerpc/kernel/asm-offsets.c

+3 −0
Original line number Diff line number Diff line
@@ -93,6 +93,9 @@ int main(void) 
	OFFSET(THREAD_INFO, task_struct, stack);

	DEFINE(THREAD_INFO_GAP, _ALIGN_UP(sizeof(struct thread_info), 16));

	OFFSET(KSP_LIMIT, thread_struct, ksp_limit);

#ifdef CONFIG_PPC_RTAS

	OFFSET(RTAS_SP, thread_struct, rtas_sp);

#endif

#endif /* CONFIG_PPC64 */



#ifdef CONFIG_LIVEPATCH

arch/powerpc/kernel/entry_32.S

+3 −2
Original line number Diff line number Diff line
@@ -1332,7 +1332,7 @@ _GLOBAL(enter_rtas) 
	MTMSRD(r0)		/* don't get trashed */

	li	r9,MSR_KERNEL & ~(MSR_IR|MSR_DR)

	mtlr	r6

	mtspr	SPRN_SPRG_RTAS,r7

	stw	r7, THREAD + RTAS_SP(r2)

	mtspr	SPRN_SRR0,r8

	mtspr	SPRN_SRR1,r9

	RFI
@@ -1341,7 +1341,8 @@ _GLOBAL(enter_rtas) 
	lwz	r9,8(r9)	/* original msr value */

	addi	r1,r1,INT_FRAME_SIZE

	li	r0,0

	mtspr	SPRN_SPRG_RTAS,r0

	tophys(r7, r2)

	stw	r0, THREAD + RTAS_SP(r7)

	mtspr	SPRN_SRR0,r8

	mtspr	SPRN_SRR1,r9

	RFI			/* return to caller */

arch/powerpc/kernel/head_32.S

+12 −10
Original line number Diff line number Diff line
@@ -352,9 +352,8 @@ i##n: \ 
 * registers that might have bad values includes all the GPRs

 * and all the BATs.  We indicate that we are in RTAS by putting

 * a non-zero value, the address of the exception frame to use,

 * in SPRG2.  The machine check handler checks SPRG2 and uses its

 * value if it is non-zero.  If we ever needed to free up SPRG2,

 * we could use a field in the thread_info or thread_struct instead.

 * in thread.rtas_sp.  The machine check handler checks thread.rtas_sp

 * and uses its value if it is non-zero.

 * (Other exception handlers assume that r1 is a valid kernel stack

 * pointer when we take an exception from supervisor mode.)

 *	-- paulus.
@@ -365,16 +364,15 @@ i##n: \ 
	mtspr	SPRN_SPRG_SCRATCH1,r11

	mfcr	r10

#ifdef CONFIG_PPC_CHRP

	mfspr	r11,SPRN_SPRG_RTAS

	cmpwi	0,r11,0

	bne	7f

	mfspr	r11, SPRN_SPRG_THREAD

	lwz	r11, RTAS_SP(r11)

	cmpwi	cr1, r11, 0

	bne	cr1, 7f

#endif /* CONFIG_PPC_CHRP */

	EXCEPTION_PROLOG_1

7:	EXCEPTION_PROLOG_2

	addi	r3,r1,STACK_FRAME_OVERHEAD

#ifdef CONFIG_PPC_CHRP

	mfspr	r4,SPRN_SPRG_RTAS

	cmpwi	cr1,r4,0

	bne	cr1,1f

#endif

	EXC_XFER_STD(0x200, machine_check_exception)
@@ -865,8 +863,10 @@ __secondary_start: 
	tophys(r4,r2)

	addi	r4,r4,THREAD	/* phys address of our thread_struct */

	mtspr	SPRN_SPRG_THREAD,r4

#ifdef CONFIG_PPC_RTAS

	li	r3,0

	mtspr	SPRN_SPRG_RTAS,r3	/* 0 => not in RTAS */

	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */

#endif



	/* enable MMU and jump to start_secondary */

	li	r4,MSR_KERNEL
@@ -950,8 +950,10 @@ start_here: 
	tophys(r4,r2)

	addi	r4,r4,THREAD	/* init task's THREAD */

	mtspr	SPRN_SPRG_THREAD,r4

#ifdef CONFIG_PPC_RTAS

	li	r3,0

	mtspr	SPRN_SPRG_RTAS,r3	/* 0 => not in RTAS */

	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */

#endif



	/* stack */

	lis	r1,init_thread_union@ha