perf counters: hw driver API

Impact: restructure code, introduce hw_ops driver abstraction

Introduce this abstraction to handle counter details:

 struct hw_perf_counter_ops {
	void (*hw_perf_counter_enable)	(struct perf_counter *counter);
	void (*hw_perf_counter_disable)	(struct perf_counter *counter);
	void (*hw_perf_counter_read)	(struct perf_counter *counter);
 };

This will be useful to support assymetric hw details, and it will also
be useful to implement "software counters". (Counters that count kernel
managed sw events such as pagefaults, context-switches, wall-clock time
or task-local time.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 66 insertions, 31 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 54b4ad0cce68..718b635dece6 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -56,7 +56,7 @@ const int max_intel_perfmon_events = ARRAY_SIZE(intel_perfmon_event_map);
 /*
  * Setup the hardware configuration for a given hw_event_type
  */
-int hw_perf_counter_init(struct perf_counter *counter)
+static int __hw_perf_counter_init(struct perf_counter *counter)
 {
         struct perf_counter_hw_event *hw_event = &counter->hw_event;
         struct hw_perf_counter *hwc = &counter->hw;
@@ -135,7 +135,7 @@ u64 hw_perf_disable_all(void)
 EXPORT_SYMBOL_GPL(hw_perf_disable_all);
 
 static inline void
-__hw_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)
+__x86_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)
 {
         wrmsr(hwc->config_base + idx, hwc->config, 0);
 }
@@ -149,13 +149,13 @@ static void __hw_perf_counter_set_period(struct hw_perf_counter *hwc, int idx)
         wrmsr(hwc->counter_base + idx, hwc->next_count, 0);
 }
 
-static void __hw_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
+static void __x86_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
 {
         wrmsr(hwc->config_base + idx,
               hwc->config | ARCH_PERFMON_EVENTSEL0_ENABLE, 0);
 }
 
-void hw_perf_counter_enable(struct perf_counter *counter)
+static void x86_perf_counter_enable(struct perf_counter *counter)
 {
         struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
         struct hw_perf_counter *hwc = &counter->hw;
@@ -170,12 +170,12 @@ void hw_perf_counter_enable(struct perf_counter *counter)
 
         perf_counters_lapic_init(hwc->nmi);
 
-        __hw_perf_counter_disable(hwc, idx);
+        __x86_perf_counter_disable(hwc, idx);
 
         cpuc->counters[idx] = counter;
 
         __hw_perf_counter_set_period(hwc, idx);
-        __hw_perf_counter_enable(hwc, idx);
+        __x86_perf_counter_enable(hwc, idx);
 }
 
 #ifdef CONFIG_X86_64
@@ -282,20 +282,20 @@ void perf_counter_print_debug(void)
         local_irq_enable();
 }
 
-void hw_perf_counter_disable(struct perf_counter *counter)
+static void x86_perf_counter_disable(struct perf_counter *counter)
 {
         struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
         struct hw_perf_counter *hwc = &counter->hw;
         unsigned int idx = hwc->idx;
 
-        __hw_perf_counter_disable(hwc, idx);
+        __x86_perf_counter_disable(hwc, idx);
 
         clear_bit(idx, cpuc->used);
         cpuc->counters[idx] = NULL;
         __hw_perf_save_counter(counter, hwc, idx);
 }
 
-void hw_perf_counter_read(struct perf_counter *counter)
+static void x86_perf_counter_read(struct perf_counter *counter)
 {
         struct hw_perf_counter *hwc = &counter->hw;
         unsigned long addr = hwc->counter_base + hwc->idx;
@@ -342,7 +342,7 @@ static void perf_save_and_restart(struct perf_counter *counter)
         __hw_perf_counter_set_period(hwc, idx);
 
         if (pmc_ctrl & ARCH_PERFMON_EVENTSEL0_ENABLE)
-                __hw_perf_counter_enable(hwc, idx);
+                __x86_perf_counter_enable(hwc, idx);
 }
 
 static void
@@ -572,3 +572,20 @@ void __init init_hw_perf_counters(void)
 
         perf_counters_initialized = true;
 }
+
+static struct hw_perf_counter_ops x86_perf_counter_ops = {
+        .hw_perf_counter_enable         = x86_perf_counter_enable,
+        .hw_perf_counter_disable        = x86_perf_counter_disable,
+        .hw_perf_counter_read           = x86_perf_counter_read,
+};
+
+struct hw_perf_counter_ops *hw_perf_counter_init(struct perf_counter *counter)
+{
+        int err;
+
+        err = __hw_perf_counter_init(counter);
+        if (err)
+                return NULL;
+
+        return &x86_perf_counter_ops;
+}
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 7af7d8965460..27385641ecb6 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -113,6 +113,17 @@ struct perf_data {
         u8                              data[PERF_DATA_BUFLEN];
 };
 
+struct perf_counter;
+
+/**
+ * struct hw_perf_counter_ops - performance counter hw ops
+ */
+struct hw_perf_counter_ops {
+        void (*hw_perf_counter_enable)  (struct perf_counter *counter);
+        void (*hw_perf_counter_disable) (struct perf_counter *counter);
+        void (*hw_perf_counter_read)    (struct perf_counter *counter);
+};
+
 /**
  * struct perf_counter - performance counter kernel representation:
  */
@@ -120,6 +131,7 @@ struct perf_counter {
         struct list_head                list_entry;
         struct list_head                sibling_list;
         struct perf_counter             *group_leader;
+        struct hw_perf_counter_ops      *hw_ops;
 
         int                             active;
 #if BITS_PER_LONG == 64
@@ -185,6 +197,9 @@ struct perf_cpu_context {
 extern int perf_max_counters;
 
 #ifdef CONFIG_PERF_COUNTERS
+extern struct hw_perf_counter_ops *
+hw_perf_counter_init(struct perf_counter *counter);
+
 extern void perf_counter_task_sched_in(struct task_struct *task, int cpu);
 extern void perf_counter_task_sched_out(struct task_struct *task, int cpu);
 extern void perf_counter_task_tick(struct task_struct *task, int cpu);
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 278209c547a8..e6e41ca95463 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -37,18 +37,15 @@ static DEFINE_MUTEX(perf_resource_mutex);
 /*
  * Architecture provided APIs - weak aliases:
  */
-
-int __weak hw_perf_counter_init(struct perf_counter *counter)
+extern __weak struct hw_perf_counter_ops *
+hw_perf_counter_init(struct perf_counter *counter)
 {
-        return -EINVAL;
+        return ERR_PTR(-EINVAL);
 }
 
-void __weak hw_perf_counter_enable(struct perf_counter *counter)         { }
-void __weak hw_perf_counter_disable(struct perf_counter *counter)        { }
-void __weak hw_perf_counter_read(struct perf_counter *counter)           { }
-void __weak hw_perf_disable_all(void) { }
-void __weak hw_perf_enable_all(void) { }
-void __weak hw_perf_counter_setup(void) { }
+void __weak hw_perf_disable_all(void)    { }
+void __weak hw_perf_enable_all(void)     { }
+void __weak hw_perf_counter_setup(void)  { }
 
 #if BITS_PER_LONG == 64
 
@@ -146,7 +143,7 @@ static void __perf_counter_remove_from_context(void *info)
         spin_lock(&ctx->lock);
 
         if (counter->active) {
-                hw_perf_counter_disable(counter);
+                counter->hw_ops->hw_perf_counter_disable(counter);
                 counter->active = 0;
                 ctx->nr_active--;
                 cpuctx->active_oncpu--;
@@ -257,7 +254,7 @@ static void __perf_install_in_context(void *info)
         ctx->nr_counters++;
 
         if (cpuctx->active_oncpu < perf_max_counters) {
-                hw_perf_counter_enable(counter);
+                counter->hw_ops->hw_perf_counter_enable(counter);
                 counter->active = 1;
                 counter->oncpu = cpu;
                 ctx->nr_active++;
@@ -333,7 +330,7 @@ counter_sched_out(struct perf_counter *counter,
         if (!counter->active)
                 return;
 
-        hw_perf_counter_disable(counter);
+        counter->hw_ops->hw_perf_counter_disable(counter);
         counter->active =  0;
         counter->oncpu  = -1;
 
@@ -392,7 +389,7 @@ counter_sched_in(struct perf_counter *counter,
                  struct perf_counter_context *ctx,
                  int cpu)
 {
-        hw_perf_counter_enable(counter);
+        counter->hw_ops->hw_perf_counter_enable(counter);
         counter->active = 1;
         counter->oncpu = cpu;   /* TODO: put 'cpu' into cpuctx->cpu */
 
@@ -509,7 +506,9 @@ void perf_counter_init_task(struct task_struct *task)
  */
 static void __hw_perf_counter_read(void *info)
 {
-        hw_perf_counter_read(info);
+        struct perf_counter *counter = info;
+
+        counter->hw_ops->hw_perf_counter_read(counter);
 }
 
 static u64 perf_counter_read(struct perf_counter *counter)
@@ -816,8 +815,10 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
                    int cpu,
                    struct perf_counter *group_leader)
 {
-        struct perf_counter *counter = kzalloc(sizeof(*counter), GFP_KERNEL);
+        struct hw_perf_counter_ops *hw_ops;
+        struct perf_counter *counter;
 
+        counter = kzalloc(sizeof(*counter), GFP_KERNEL);
         if (!counter)
                 return NULL;
 
@@ -839,6 +840,14 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
         counter->hw_event               = *hw_event;
         counter->wakeup_pending         = 0;
         counter->group_leader           = group_leader;
+        counter->hw_ops                 = NULL;
+
+        hw_ops = hw_perf_counter_init(counter);
+        if (!hw_ops) {
+                kfree(counter);
+                return NULL;
+        }
+        counter->hw_ops = hw_ops;
 
         return counter;
 }
@@ -908,10 +917,6 @@ asmlinkage int sys_perf_counter_open(
         if (!counter)
                 goto err_put_context;
 
-        ret = hw_perf_counter_init(counter);
-        if (ret)
-                goto err_free_put_context;
-
         perf_install_in_context(ctx, counter, cpu);
 
         ret = anon_inode_getfd("[perf_counter]", &perf_fops, counter, 0);
@@ -927,8 +932,6 @@ err_remove_free_put_context:
         mutex_lock(&counter->mutex);
         perf_counter_remove_from_context(counter);
         mutex_unlock(&counter->mutex);
-
-err_free_put_context:
         kfree(counter);
 
 err_put_context: