From 330a1eb7775ba876dbd46b9885556e57f705e3d4 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 28 Jun 2013 18:15:16 +1000 Subject: powerpc/perf: Core EBB support for 64-bit book3s Add support for EBB (Event Based Branches) on 64-bit book3s. See the included documentation for more details. EBBs are a feature which allows the hardware to branch directly to a specified user space address when a PMU event overflows. This can be used by programs for self-monitoring with no kernel involvement in the inner loop. Most of the logic is in the generic book3s code, primarily to avoid a proliferation of PMU callbacks. Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/perf/core-book3s.c | 161 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 148 insertions(+), 13 deletions(-) (limited to 'arch/powerpc/perf') diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index c91dc43..a3985ae 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -77,6 +77,9 @@ static unsigned int freeze_events_kernel = MMCR0_FCS; #define MMCR0_PMCjCE MMCR0_PMCnCE #define MMCR0_FC56 0 #define MMCR0_PMAO 0 +#define MMCR0_EBE 0 +#define MMCR0_PMCC 0 +#define MMCR0_PMCC_U6 0 #define SPRN_MMCRA SPRN_MMCR2 #define MMCRA_SAMPLE_ENABLE 0 @@ -104,6 +107,15 @@ static inline int siar_valid(struct pt_regs *regs) return 1; } +static bool is_ebb_event(struct perf_event *event) { return false; } +static int ebb_event_check(struct perf_event *event) { return 0; } +static void ebb_event_add(struct perf_event *event) { } +static void ebb_switch_out(unsigned long mmcr0) { } +static unsigned long ebb_switch_in(bool ebb, unsigned long mmcr0) +{ + return mmcr0; +} + static inline void power_pmu_bhrb_enable(struct perf_event *event) {} static inline void power_pmu_bhrb_disable(struct perf_event *event) {} void power_pmu_flush_branch_stack(void) {} @@ -464,6 +476,89 @@ void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw) return; } +static bool is_ebb_event(struct perf_event *event) +{ + /* + * This could be a per-PMU callback, but we'd rather avoid the cost. We + * check that the PMU supports EBB, meaning those that don't can still + * use bit 63 of the event code for something else if they wish. + */ + return (ppmu->flags & PPMU_EBB) && + ((event->attr.config >> EVENT_CONFIG_EBB_SHIFT) & 1); +} + +static int ebb_event_check(struct perf_event *event) +{ + struct perf_event *leader = event->group_leader; + + /* Event and group leader must agree on EBB */ + if (is_ebb_event(leader) != is_ebb_event(event)) + return -EINVAL; + + if (is_ebb_event(event)) { + if (!(event->attach_state & PERF_ATTACH_TASK)) + return -EINVAL; + + if (!leader->attr.pinned || !leader->attr.exclusive) + return -EINVAL; + + if (event->attr.inherit || event->attr.sample_period || + event->attr.enable_on_exec || event->attr.freq) + return -EINVAL; + } + + return 0; +} + +static void ebb_event_add(struct perf_event *event) +{ + if (!is_ebb_event(event) || current->thread.used_ebb) + return; + + /* + * IFF this is the first time we've added an EBB event, set + * PMXE in the user MMCR0 so we can detect when it's cleared by + * userspace. We need this so that we can context switch while + * userspace is in the EBB handler (where PMXE is 0). + */ + current->thread.used_ebb = 1; + current->thread.mmcr0 |= MMCR0_PMXE; +} + +static void ebb_switch_out(unsigned long mmcr0) +{ + if (!(mmcr0 & MMCR0_EBE)) + return; + + current->thread.siar = mfspr(SPRN_SIAR); + current->thread.sier = mfspr(SPRN_SIER); + current->thread.sdar = mfspr(SPRN_SDAR); + current->thread.mmcr0 = mmcr0 & MMCR0_USER_MASK; + current->thread.mmcr2 = mfspr(SPRN_MMCR2) & MMCR2_USER_MASK; +} + +static unsigned long ebb_switch_in(bool ebb, unsigned long mmcr0) +{ + if (!ebb) + goto out; + + /* Enable EBB and read/write to all 6 PMCs for userspace */ + mmcr0 |= MMCR0_EBE | MMCR0_PMCC_U6; + + /* Add any bits from the user reg, FC or PMAO */ + mmcr0 |= current->thread.mmcr0; + + /* Be careful not to set PMXE if userspace had it cleared */ + if (!(current->thread.mmcr0 & MMCR0_PMXE)) + mmcr0 &= ~MMCR0_PMXE; + + mtspr(SPRN_SIAR, current->thread.siar); + mtspr(SPRN_SIER, current->thread.sier); + mtspr(SPRN_SDAR, current->thread.sdar); + mtspr(SPRN_MMCR2, current->thread.mmcr2); +out: + return mmcr0; +} #endif /* CONFIG_PPC64 */ static void perf_event_interrupt(struct pt_regs *regs); @@ -734,6 +829,13 @@ static void power_pmu_read(struct perf_event *event) if (!event->hw.idx) return; + + if (is_ebb_event(event)) { + val = read_pmc(event->hw.idx); + local64_set(&event->hw.prev_count, val); + return; + } + /* * Performance monitor interrupts come even when interrupts * are soft-disabled, as long as interrupts are hard-enabled. @@ -854,7 +956,7 @@ static void write_mmcr0(struct cpu_hw_events *cpuhw, unsigned long mmcr0) static void power_pmu_disable(struct pmu *pmu) { struct cpu_hw_events *cpuhw; - unsigned long flags, val; + unsigned long flags, mmcr0, val; if (!ppmu) return; @@ -871,11 +973,11 @@ static void power_pmu_disable(struct pmu *pmu) } /* - * Set the 'freeze counters' bit, clear PMAO/FC56. + * Set the 'freeze counters' bit, clear EBE/PMCC/PMAO/FC56. */ - val = mfspr(SPRN_MMCR0); + val = mmcr0 = mfspr(SPRN_MMCR0); val |= MMCR0_FC; - val &= ~(MMCR0_PMAO | MMCR0_FC56); + val &= ~(MMCR0_EBE | MMCR0_PMCC | MMCR0_PMAO | MMCR0_FC56); /* * The barrier is to make sure the mtspr has been @@ -896,7 +998,10 @@ static void power_pmu_disable(struct pmu *pmu) cpuhw->disabled = 1; cpuhw->n_added = 0; + + ebb_switch_out(mmcr0); } + local_irq_restore(flags); } @@ -911,15 +1016,15 @@ static void power_pmu_enable(struct pmu *pmu) struct cpu_hw_events *cpuhw; unsigned long flags; long i; - unsigned long val; + unsigned long val, mmcr0; s64 left; unsigned int hwc_index[MAX_HWEVENTS]; int n_lim; int idx; + bool ebb; if (!ppmu) return; - local_irq_save(flags); cpuhw = &__get_cpu_var(cpu_hw_events); @@ -934,6 +1039,13 @@ static void power_pmu_enable(struct pmu *pmu) cpuhw->disabled = 0; /* + * EBB requires an exclusive group and all events must have the EBB + * flag set, or not set, so we can just check a single event. Also we + * know we have at least one event. + */ + ebb = is_ebb_event(cpuhw->event[0]); + + /* * If we didn't change anything, or only removed events, * no need to recalculate MMCR* settings and reset the PMCs. * Just reenable the PMU with the current MMCR* settings @@ -1008,25 +1120,34 @@ static void power_pmu_enable(struct pmu *pmu) ++n_lim; continue; } - val = 0; - if (event->hw.sample_period) { - left = local64_read(&event->hw.period_left); - if (left < 0x80000000L) - val = 0x80000000L - left; + + if (ebb) + val = local64_read(&event->hw.prev_count); + else { + val = 0; + if (event->hw.sample_period) { + left = local64_read(&event->hw.period_left); + if (left < 0x80000000L) + val = 0x80000000L - left; + } + local64_set(&event->hw.prev_count, val); } - local64_set(&event->hw.prev_count, val); + event->hw.idx = idx; if (event->hw.state & PERF_HES_STOPPED) val = 0; write_pmc(idx, val); + perf_event_update_userpage(event); } cpuhw->n_limited = n_lim; cpuhw->mmcr[0] |= MMCR0_PMXE | MMCR0_FCECE; out_enable: + mmcr0 = ebb_switch_in(ebb, cpuhw->mmcr[0]); + mb(); - write_mmcr0(cpuhw, cpuhw->mmcr[0]); + write_mmcr0(cpuhw, mmcr0); /* * Enable instruction sampling if necessary @@ -1124,6 +1245,8 @@ static int power_pmu_add(struct perf_event *event, int ef_flags) event->hw.config = cpuhw->events[n0]; nocheck: + ebb_event_add(event); + ++cpuhw->n_events; ++cpuhw->n_added; @@ -1484,6 +1607,11 @@ static int power_pmu_event_init(struct perf_event *event) } } + /* Extra checks for EBB */ + err = ebb_event_check(event); + if (err) + return err; + /* * If this is in a group, check if it can go on with all the * other hardware events in the group. We assume the event @@ -1523,6 +1651,13 @@ static int power_pmu_event_init(struct perf_event *event) local64_set(&event->hw.period_left, event->hw.last_period); /* + * For EBB events we just context switch the PMC value, we don't do any + * of the sample_period logic. We use hw.prev_count for this. + */ + if (is_ebb_event(event)) + local64_set(&event->hw.prev_count, 0); + + /* * See if we need to reserve the PMU. * If no events are currently in use, then we have to take a * mutex to ensure that we don't race with another task doing -- cgit v1.1