perf, x86: Fix AMD hotplug & constraint initialization

Commit 3f6da39 ("perf: Rework and fix the arch CPU-hotplug hooks") moved
the amd northbridge allocation from CPUS_ONLINE to CPUS_PREPARE_UP
however amd_nb_id() doesn't work yet on prepare so it would simply bail
basically reverting to a state where we do not properly track node wide
constraints - causing weird perf results.

Fix up the AMD NorthBridge initialization code by allocating from
CPU_UP_PREPARE and installing it from CPU_STARTING once we have the
proper nb_id. It also properly deals with the allocation failing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ robustify using amd_has_nb() ]
Signed-off-by: Stephane Eranian <eranian@google.com>
LKML-Reference: <1269353485.5109.48.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 47 insertions, 33 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index b87e0b6970cb..db6f7d4056e1 100644
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -137,6 +137,13 @@ static inline int amd_is_nb_event(struct hw_perf_event *hwc)
         return (hwc->config & 0xe0) == 0xe0;
 }
 
+static inline int amd_has_nb(struct cpu_hw_events *cpuc)
+{
+        struct amd_nb *nb = cpuc->amd_nb;
+
+        return nb && nb->nb_id != -1;
+}
+
 static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
                                       struct perf_event *event)
 {
@@ -147,7 +154,7 @@ static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
         /*
          * only care about NB events
          */
-        if (!(nb && amd_is_nb_event(hwc)))
+        if (!(amd_has_nb(cpuc) && amd_is_nb_event(hwc)))
                 return;
 
         /*
@@ -214,7 +221,7 @@ amd_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
         /*
          * if not NB event or no NB, then no constraints
          */
-        if (!(nb && amd_is_nb_event(hwc)))
+        if (!(amd_has_nb(cpuc) && amd_is_nb_event(hwc)))
                 return &unconstrained;
 
         /*
@@ -293,51 +300,55 @@ static struct amd_nb *amd_alloc_nb(int cpu, int nb_id)
         return nb;
 }
 
-static void amd_pmu_cpu_online(int cpu)
+static int amd_pmu_cpu_prepare(int cpu)
+{
+        struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+
+        WARN_ON_ONCE(cpuc->amd_nb);
+
+        if (boot_cpu_data.x86_max_cores < 2)
+                return NOTIFY_OK;
+
+        cpuc->amd_nb = amd_alloc_nb(cpu, -1);
+        if (!cpuc->amd_nb)
+                return NOTIFY_BAD;
+
+        return NOTIFY_OK;
+}
+
+static void amd_pmu_cpu_starting(int cpu)
 {
-        struct cpu_hw_events *cpu1, *cpu2;
-        struct amd_nb *nb = NULL;
+        struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+        struct amd_nb *nb;
         int i, nb_id;
 
         if (boot_cpu_data.x86_max_cores < 2)
                 return;
 
-        /*
-         * function may be called too early in the
-         * boot process, in which case nb_id is bogus
-         */
         nb_id = amd_get_nb_id(cpu);
-        if (nb_id == BAD_APICID)
-                return;
-
-        cpu1 = &per_cpu(cpu_hw_events, cpu);
-        cpu1->amd_nb = NULL;
+        WARN_ON_ONCE(nb_id == BAD_APICID);
 
         raw_spin_lock(&amd_nb_lock);
 
         for_each_online_cpu(i) {
-                cpu2 = &per_cpu(cpu_hw_events, i);
-                nb = cpu2->amd_nb;
-                if (!nb)
+                nb = per_cpu(cpu_hw_events, i).amd_nb;
+                if (WARN_ON_ONCE(!nb))
                         continue;
-                if (nb->nb_id == nb_id)
-                        goto found;
-        }
 
-        nb = amd_alloc_nb(cpu, nb_id);
-        if (!nb) {
-                pr_err("perf_events: failed NB allocation for CPU%d\n", cpu);
-                raw_spin_unlock(&amd_nb_lock);
-                return;
+                if (nb->nb_id == nb_id) {
+                        kfree(cpuc->amd_nb);
+                        cpuc->amd_nb = nb;
+                        break;
+                }
         }
-found:
-        nb->refcnt++;
-        cpu1->amd_nb = nb;
+
+        cpuc->amd_nb->nb_id = nb_id;
+        cpuc->amd_nb->refcnt++;
 
         raw_spin_unlock(&amd_nb_lock);
 }
 
-static void amd_pmu_cpu_offline(int cpu)
+static void amd_pmu_cpu_dead(int cpu)
 {
         struct cpu_hw_events *cpuhw;
 
@@ -349,8 +360,10 @@ static void amd_pmu_cpu_offline(int cpu)
         raw_spin_lock(&amd_nb_lock);
 
         if (cpuhw->amd_nb) {
-                if (--cpuhw->amd_nb->refcnt == 0)
-                        kfree(cpuhw->amd_nb);
+                struct amd_nb *nb = cpuhw->amd_nb;
+
+                if (nb->nb_id == -1 || --nb->refcnt == 0)
+                        kfree(nb);
 
                 cpuhw->amd_nb = NULL;
         }
@@ -379,8 +392,9 @@ static __initconst struct x86_pmu amd_pmu = {
         .get_event_constraints  = amd_get_event_constraints,
         .put_event_constraints  = amd_put_event_constraints,
 
-        .cpu_prepare            = amd_pmu_cpu_online,
-        .cpu_dead               = amd_pmu_cpu_offline,
+        .cpu_prepare            = amd_pmu_cpu_prepare,
+        .cpu_starting           = amd_pmu_cpu_starting,
+        .cpu_dead               = amd_pmu_cpu_dead,
 };
 
 static __init int amd_pmu_init(void)