Commit 0837e324 authored by Anton Blanchard's avatar Anton Blanchard Committed by Ingo Molnar

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
...@@ -880,6 +880,7 @@ ...@@ -880,6 +880,7 @@
#define PV_970 0x0039 #define PV_970 0x0039
#define PV_POWER5 0x003A #define PV_POWER5 0x003A
#define PV_POWER5p 0x003B #define PV_POWER5p 0x003B
#define PV_POWER7 0x003F
#define PV_970FX 0x003C #define PV_970FX 0x003C
#define PV_630 0x0040 #define PV_630 0x0040
#define PV_630p 0x0041 #define PV_630p 0x0041
......
...@@ -1269,6 +1269,28 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs) ...@@ -1269,6 +1269,28 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)
return ip; 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 * Performance monitor interrupt stuff
*/ */
...@@ -1316,7 +1338,7 @@ static void perf_event_interrupt(struct pt_regs *regs) ...@@ -1316,7 +1338,7 @@ static void perf_event_interrupt(struct pt_regs *regs)
if (is_limited_pmc(i + 1)) if (is_limited_pmc(i + 1))
continue; continue;
val = read_pmc(i + 1); val = read_pmc(i + 1);
if ((int)val < 0) if (pmc_overflow(val))
write_pmc(i + 1, 0); write_pmc(i + 1, 0);
} }
} }
......
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