Commit bc09c219 authored by Michael Neuling's avatar Michael Neuling Committed by Benjamin Herrenschmidt

powerpc/perf: Fix finding overflowed PMC in interrupt

If a PMC is about to overflow on a counter that's on an active perf event
(ie. less than 256 from the end) and a _different_ PMC overflows just at this
time (a PMC that's not on an active perf event), we currently mark the event as
found, but in reality it's not as it's likely the other PMC that caused the
IRQ.  Since we mark it as found the second catch all for overflows doesn't run,
and we don't reset the overflowing PMC ever.  Hence we keep hitting that same
PMC IRQ over and over and don't reset the actual overflowing counter.

This is a rewrite of the perf interrupt handler for book3s to get around this.
We now check to see if any of the PMCs have actually overflowed (ie >=
0x80000000).  If yes, record it for active counters and just reset it for
inactive counters.  If it's not overflowed, then we check to see if it's one of
the buggy power7 counters and if it is, record it and continue.  If none of the
PMCs match this, then we make note that we couldn't find the PMC that caused
the IRQ.
Signed-off-by: default avatarMichael Neuling <mikey@neuling.org>
Reviewed-by: default avatarSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
cc: Paul Mackerras <paulus@samba.org>
cc: Anton Blanchard <anton@samba.org>
cc: Linux PPC dev <linuxppc-dev@ozlabs.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 6a040ce7
...@@ -1412,11 +1412,8 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs) ...@@ -1412,11 +1412,8 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)
return regs->nip; return regs->nip;
} }
static bool pmc_overflow(unsigned long val) static bool pmc_overflow_power7(unsigned long val)
{ {
if ((int)val < 0)
return true;
/* /*
* Events on POWER7 can roll back if a speculative event doesn't * Events on POWER7 can roll back if a speculative event doesn't
* eventually complete. Unfortunately in some rare cases they will * eventually complete. Unfortunately in some rare cases they will
...@@ -1428,7 +1425,15 @@ static bool pmc_overflow(unsigned long val) ...@@ -1428,7 +1425,15 @@ static bool pmc_overflow(unsigned long val)
* PMCs because a user might set a period of less than 256 and we * PMCs because a user might set a period of less than 256 and we
* don't want to mistakenly reset them. * don't want to mistakenly reset them.
*/ */
if (pvr_version_is(PVR_POWER7) && ((0x80000000 - val) <= 256)) if ((0x80000000 - val) <= 256)
return true;
return false;
}
static bool pmc_overflow(unsigned long val)
{
if ((int)val < 0)
return true; return true;
return false; return false;
...@@ -1439,11 +1444,11 @@ static bool pmc_overflow(unsigned long val) ...@@ -1439,11 +1444,11 @@ static bool pmc_overflow(unsigned long val)
*/ */
static void perf_event_interrupt(struct pt_regs *regs) static void perf_event_interrupt(struct pt_regs *regs)
{ {
int i; int i, j;
struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events); struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
struct perf_event *event; struct perf_event *event;
unsigned long val; unsigned long val[8];
int found = 0; int found, active;
int nmi; int nmi;
if (cpuhw->n_limited) if (cpuhw->n_limited)
...@@ -1458,33 +1463,53 @@ static void perf_event_interrupt(struct pt_regs *regs) ...@@ -1458,33 +1463,53 @@ static void perf_event_interrupt(struct pt_regs *regs)
else else
irq_enter(); irq_enter();
for (i = 0; i < cpuhw->n_events; ++i) { /* Read all the PMCs since we'll need them a bunch of times */
event = cpuhw->event[i]; for (i = 0; i < ppmu->n_counter; ++i)
if (!event->hw.idx || is_limited_pmc(event->hw.idx)) val[i] = read_pmc(i + 1);
/* Try to find what caused the IRQ */
found = 0;
for (i = 0; i < ppmu->n_counter; ++i) {
if (!pmc_overflow(val[i]))
continue; continue;
val = read_pmc(event->hw.idx); if (is_limited_pmc(i + 1))
if ((int)val < 0) { continue; /* these won't generate IRQs */
/* event has overflowed */ /*
found = 1; * We've found one that's overflowed. For active
record_and_restart(event, val, regs); * counters we need to log this. For inactive
* counters, we need to reset it anyway
*/
found = 1;
active = 0;
for (j = 0; j < cpuhw->n_events; ++j) {
event = cpuhw->event[j];
if (event->hw.idx == (i + 1)) {
active = 1;
record_and_restart(event, val[i], regs);
break;
}
} }
if (!active)
/* reset non active counters that have overflowed */
write_pmc(i + 1, 0);
} }
if (!found && pvr_version_is(PVR_POWER7)) {
/* /* check active counters for special buggy p7 overflow */
* In case we didn't find and reset the event that caused for (i = 0; i < cpuhw->n_events; ++i) {
* the interrupt, scan all events and reset any that are event = cpuhw->event[i];
* negative, to avoid getting continual interrupts. if (!event->hw.idx || is_limited_pmc(event->hw.idx))
* Any that we processed in the previous loop will not be negative.
*/
if (!found) {
for (i = 0; i < ppmu->n_counter; ++i) {
if (is_limited_pmc(i + 1))
continue; continue;
val = read_pmc(i + 1); if (pmc_overflow_power7(val[event->hw.idx - 1])) {
if (pmc_overflow(val)) /* event has overflowed in a buggy way*/
write_pmc(i + 1, 0); found = 1;
record_and_restart(event,
val[event->hw.idx - 1],
regs);
}
} }
} }
if ((!found) && printk_ratelimit())
printk(KERN_WARNING "Can't find PMC that caused IRQ\n");
/* /*
* Reset MMCR0 to its normal value. This will set PMXE and * Reset MMCR0 to its normal value. This will set PMXE and
......
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