diff options
| author | Anton Blanchard <anton@samba.org> | 2011-03-09 14:38:42 +1100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-03-16 14:04:13 +0100 |
| commit | 0837e3242c73566fc1c0196b4ec61779c25ffc93 (patch) | |
| tree | db77cdc93b99b1433b73a461f44543983af746bc | |
| parent | 7d5d02dadd43db7f829775e404e82019c5d5586f (diff) | |
| download | linux-0837e3242c73566fc1c0196b4ec61779c25ffc93.tar.bz2 | |
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: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter 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: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/powerpc/include/asm/reg.h | 1 | ||||
| -rw-r--r-- | arch/powerpc/kernel/perf_event.c | 24 |
2 files changed, 24 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index 125fc1ad665d..7626fa78e1f8 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -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 diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c index ab6f6beadb57..97e0ae414940 100644 --- a/arch/powerpc/kernel/perf_event.c +++ b/arch/powerpc/kernel/perf_event.c @@ -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); } } |