powerpc/pseries: Use jump labels for hcall tracepoints

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hcall tracepoints add quite a few instructions to our hcall path:

plpar_hcall:
	mr      r2,r2
	mfcr    r0
	stw     r0,8(r1)
	b       164		<---- start
	ld      r12,0(r2)
	std     r12,32(r1)
	cmpdi   r12,0
	beq     164		<---- end
...

We have an unconditional branch that gets noped out during boot and
a load/compare/branch. We also store the tracepoint value to the
stack for the hcall_exit path to use.

By using jump labels we can simplify this to just a single nop that
gets replaced with a branch when the tracepoint is enabled:

plpar_hcall:
	mr      r2,r2
	mfcr    r0
	stw     r0,8(r1)
	nop			<----
...

If jump labels are not enabled, we fall back to the old method.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

...

This commit is contained in:

Anton Blanchard 2014-07-03 15:52:03 +10:00 • committed by Benjamin Herrenschmidt

parent 8fa5d4547e

commit cc1adb5f32

3 changed files with 142 additions and 41 deletions

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9

arch/powerpc/include/asm/jump_label.h

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144

arch/powerpc/platforms/pseries/hvCall.S

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30

arch/powerpc/platforms/pseries/lpar.c

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