perf/x86: Enable overflow on Intel KNC with a custom knc_pmu_handle_irq()

Although based on the Intel P6 design, the interrupt mechnanism
for KNC more closely resembles the Intel architectural
perfmon one.

We can't just re-use that code though, because KNC has different
MSR numbers for the status and ack registers.

In this case we just cut-and paste from perf_event_intel.c
with some minor changes, as it looks like it would not be
worth the trouble to change that code to be MSR-configurable.

Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: eranian@gmail.com
Cc: Meadows Lawrence F <lawrence.f.meadows@intel.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1210171304410.23243@vincent-weaver-1.um.maine.edu
[ Small stylistic edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 77 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_knc.c b/arch/x86/kernel/cpu/perf_event_knc.c
index f3a2af41552d..4b7731bf23a8 100644
--- a/arch/x86/kernel/cpu/perf_event_knc.c
+++ b/arch/x86/kernel/cpu/perf_event_knc.c
@@ -3,6 +3,8 @@
 #include <linux/perf_event.h>
 #include <linux/types.h>
 
+#include <asm/hardirq.h>
+
 #include "perf_event.h"
 
 static const u64 knc_perfmon_event_map[] =
@@ -193,6 +195,80 @@ static void knc_pmu_enable_event(struct perf_event *event)
         (void)wrmsrl_safe(hwc->config_base + hwc->idx, val);
 }
 
+static inline u64 knc_pmu_get_status(void)
+{
+        u64 status;
+
+        rdmsrl(MSR_KNC_IA32_PERF_GLOBAL_STATUS, status);
+
+        return status;
+}
+
+static inline void knc_pmu_ack_status(u64 ack)
+{
+        wrmsrl(MSR_KNC_IA32_PERF_GLOBAL_OVF_CONTROL, ack);
+}
+
+static int knc_pmu_handle_irq(struct pt_regs *regs)
+{
+        struct perf_sample_data data;
+        struct cpu_hw_events *cpuc;
+        int handled = 0;
+        int bit, loops;
+        u64 status;
+
+        cpuc = &__get_cpu_var(cpu_hw_events);
+
+        knc_pmu_disable_all();
+
+        status = knc_pmu_get_status();
+        if (!status) {
+                knc_pmu_enable_all(0);
+                return handled;
+        }
+
+        loops = 0;
+again:
+        knc_pmu_ack_status(status);
+        if (++loops > 100) {
+                WARN_ONCE(1, "perf: irq loop stuck!\n");
+                perf_event_print_debug();
+                goto done;
+        }
+
+        inc_irq_stat(apic_perf_irqs);
+
+        for_each_set_bit(bit, (unsigned long *)&status, X86_PMC_IDX_MAX) {
+                struct perf_event *event = cpuc->events[bit];
+
+                handled++;
+
+                if (!test_bit(bit, cpuc->active_mask))
+                        continue;
+
+                if (!intel_pmu_save_and_restart(event))
+                        continue;
+
+                perf_sample_data_init(&data, 0, event->hw.last_period);
+
+                if (perf_event_overflow(event, &data, regs))
+                        x86_pmu_stop(event, 0);
+        }
+
+        /*
+         * Repeat if there is more work to be done:
+         */
+        status = knc_pmu_get_status();
+        if (status)
+                goto again;
+
+done:
+        knc_pmu_enable_all(0);
+
+        return handled;
+}
+
+
 PMU_FORMAT_ATTR(event,  "config:0-7"    );
 PMU_FORMAT_ATTR(umask,  "config:8-15"   );
 PMU_FORMAT_ATTR(edge,   "config:18"     );
@@ -210,7 +286,7 @@ static struct attribute *intel_knc_formats_attr[] = {
 
 static __initconst struct x86_pmu knc_pmu = {
         .name                   = "knc",
-        .handle_irq             = x86_pmu_handle_irq,
+        .handle_irq             = knc_pmu_handle_irq,
         .disable_all            = knc_pmu_disable_all,
         .enable_all             = knc_pmu_enable_all,
         .enable                 = knc_pmu_enable_event,