Commit 01f3880d authored by Michael Ellerman's avatar Michael Ellerman Committed by Paul Mackerras
Browse files

powerpc: Streamline ret_from_except_lite for non-iSeries platforms 



There is a small passage of code in ret_from_except_lite which is
only required on iSeries.  For a multi-platform kernel on non-iSeries
machines this means we end up executing ~15 nops in ret_from_except_lite.

It would be nicer if non-iSeries could skip the code entirely, and on
iSeries we can jump out of line to execute the code.

I have no performance numbers to justify this, other than the assertion
that executing 15 nops takes longer than executing 0.

Signed-off-by: default avatarMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent cd5aeb9f

arch/powerpc/kernel/entry_64.S

+29 −24
Original line number Diff line number Diff line
@@ -512,31 +512,12 @@ _GLOBAL(ret_from_except_lite) 
#endif



restore:

	ld	r5,SOFTE(r1)

#ifdef CONFIG_PPC_ISERIES

BEGIN_FW_FTR_SECTION

	cmpdi	0,r5,0

	beq	4f

	/* Check for pending interrupts (iSeries) */

	ld	r3,PACALPPACAPTR(r13)

	ld	r3,LPPACAANYINT(r3)

	cmpdi	r3,0

	beq+	4f			/* skip do_IRQ if no interrupts */



	li	r3,0

	stb	r3,PACASOFTIRQEN(r13)	/* ensure we are soft-disabled */

#ifdef CONFIG_TRACE_IRQFLAGS

	bl	.trace_hardirqs_off

	mfmsr	r10

#endif

	ori	r10,r10,MSR_EE

	mtmsrd	r10			/* hard-enable again */

	addi	r3,r1,STACK_FRAME_OVERHEAD

	bl	.do_IRQ

	b	.ret_from_except_lite		/* loop back and handle more */

4:

END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)

#endif

	ld	r5,SOFTE(r1)

FW_FTR_SECTION_ELSE

	b	iseries_check_pending_irqs

ALT_FW_FTR_SECTION_END_IFCLR(FW_FEATURE_ISERIES)

2:

	TRACE_AND_RESTORE_IRQ(r5);



	/* extract EE bit and use it to restore paca->hard_enabled */
@@ -592,6 +573,30 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES) 
	rfid

	b	.	/* prevent speculative execution */



iseries_check_pending_irqs:

#ifdef CONFIG_PPC_ISERIES

	ld	r5,SOFTE(r1)

	cmpdi	0,r5,0

	beq	2b

	/* Check for pending interrupts (iSeries) */

	ld	r3,PACALPPACAPTR(r13)

	ld	r3,LPPACAANYINT(r3)

	cmpdi	r3,0

	beq+	2b			/* skip do_IRQ if no interrupts */



	li	r3,0

	stb	r3,PACASOFTIRQEN(r13)	/* ensure we are soft-disabled */

#ifdef CONFIG_TRACE_IRQFLAGS

	bl	.trace_hardirqs_off

	mfmsr	r10

#endif

	ori	r10,r10,MSR_EE

	mtmsrd	r10			/* hard-enable again */

	addi	r3,r1,STACK_FRAME_OVERHEAD

	bl	.do_IRQ

	b	.ret_from_except_lite		/* loop back and handle more */

#endif



do_work:

#ifdef CONFIG_PREEMPT

	andi.	r0,r3,MSR_PR	/* Returning to user mode? */

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