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Commit 0837e324 authored by Anton Blanchard's avatar Anton Blanchard Committed by Ingo Molnar
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perf, powerpc: Handle events that raise an exception without overflowing 



Events on POWER7 can roll back if a speculative event doesn't
eventually complete. Unfortunately in some rare cases they will
raise a performance monitor exception. We need to catch this to
ensure we reset the PMC. In all cases the PMC will be 256 or less
cycles from overflow.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org> # as far back as it applies cleanly
LKML-Reference: <20110309143842.6c22845e@kryten>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7d5d02da

arch/powerpc/include/asm/reg.h

+1 −0
Original line number Diff line number Diff line
@@ -880,6 +880,7 @@ 
#define PV_970		0x0039

#define PV_POWER5	0x003A

#define PV_POWER5p	0x003B

#define PV_POWER7	0x003F

#define PV_970FX	0x003C

#define PV_630		0x0040

#define PV_630p	0x0041

arch/powerpc/kernel/perf_event.c

+23 −1
Original line number Diff line number Diff line
@@ -1269,6 +1269,28 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs) 
	return ip;

}



static bool pmc_overflow(unsigned long val)

{

	if ((int)val < 0)

		return true;



	/*

	 * Events on POWER7 can roll back if a speculative event doesn't

	 * eventually complete. Unfortunately in some rare cases they will

	 * raise a performance monitor exception. We need to catch this to

	 * ensure we reset the PMC. In all cases the PMC will be 256 or less

	 * cycles from overflow.

	 *

	 * We only do this if the first pass fails to find any overflowing

	 * PMCs because a user might set a period of less than 256 and we

	 * don't want to mistakenly reset them.

	 */

	if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256))

		return true;



	return false;

}



/*

 * Performance monitor interrupt stuff

 */
@@ -1316,7 +1338,7 @@ static void perf_event_interrupt(struct pt_regs *regs) 
			if (is_limited_pmc(i + 1))

				continue;

			val = read_pmc(i + 1);

			if ((int)val < 0)

			if (pmc_overflow(val))

				write_pmc(i + 1, 0);

		}

	}