1 files changed, 663 insertions, 258 deletions

diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index 87b67e3a765a..48bfe1386038 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -19,45 +19,61 @@
  * Markus Metzger <markus.t.metzger@intel.com>, 2007-2009
  */
 
-
-#include <asm/ds.h>
-
-#include <linux/errno.h>
+#include <linux/kernel.h>
 #include <linux/string.h>
-#include <linux/slab.h>
+#include <linux/errno.h>
 #include <linux/sched.h>
+#include <linux/slab.h>
 #include <linux/mm.h>
-#include <linux/kernel.h>
+#include <linux/trace_clock.h>
+
+#include <asm/ds.h>
 
+#include "ds_selftest.h"
 
 /*
- * The configuration for a particular DS hardware implementation.
+ * The configuration for a particular DS hardware implementation:
  */
 struct ds_configuration {
-        /* the name of the configuration */
-        const char *name;
-        /* the size of one pointer-typed field in the DS structure and
-           in the BTS and PEBS buffers in bytes;
-           this covers the first 8 DS fields related to buffer management. */
-        unsigned char  sizeof_field;
-        /* the size of a BTS/PEBS record in bytes */
-        unsigned char  sizeof_rec[2];
-        /* a series of bit-masks to control various features indexed
-         * by enum ds_feature */
-        unsigned long ctl[dsf_ctl_max];
+        /* The name of the configuration: */
+        const char              *name;
+
+        /* The size of pointer-typed fields in DS, BTS, and PEBS: */
+        unsigned char           sizeof_ptr_field;
+
+        /* The size of a BTS/PEBS record in bytes: */
+        unsigned char           sizeof_rec[2];
+
+        /* The number of pebs counter reset values in the DS structure. */
+        unsigned char           nr_counter_reset;
+
+        /* Control bit-masks indexed by enum ds_feature: */
+        unsigned long           ctl[dsf_ctl_max];
 };
-static DEFINE_PER_CPU(struct ds_configuration, ds_cfg_array);
+static struct ds_configuration ds_cfg __read_mostly;
+
+
+/* Maximal size of a DS configuration: */
+#define MAX_SIZEOF_DS           0x80
 
-#define ds_cfg per_cpu(ds_cfg_array, smp_processor_id())
+/* Maximal size of a BTS record: */
+#define MAX_SIZEOF_BTS          (3 * 8)
 
-#define MAX_SIZEOF_DS (12 * 8)  /* maximal size of a DS configuration */
-#define MAX_SIZEOF_BTS (3 * 8)  /* maximal size of a BTS record */
-#define DS_ALIGNMENT (1 << 3)   /* BTS and PEBS buffer alignment */
+/* BTS and PEBS buffer alignment: */
+#define DS_ALIGNMENT            (1 << 3)
 
-#define BTS_CONTROL \
- (ds_cfg.ctl[dsf_bts] | ds_cfg.ctl[dsf_bts_kernel] | ds_cfg.ctl[dsf_bts_user] |\
-  ds_cfg.ctl[dsf_bts_overflow])
+/* Number of buffer pointers in DS: */
+#define NUM_DS_PTR_FIELDS       8
 
+/* Size of a pebs reset value in DS: */
+#define PEBS_RESET_FIELD_SIZE   8
+
+/* Mask of control bits in the DS MSR register: */
+#define BTS_CONTROL                               \
+        ( ds_cfg.ctl[dsf_bts]                   | \
+          ds_cfg.ctl[dsf_bts_kernel]            | \
+          ds_cfg.ctl[dsf_bts_user]              | \
+          ds_cfg.ctl[dsf_bts_overflow] )
 
 /*
  * A BTS or PEBS tracer.
@@ -66,29 +82,36 @@ static DEFINE_PER_CPU(struct ds_configuration, ds_cfg_array);
  * to identify tracers.
  */
 struct ds_tracer {
-        /* the DS context (partially) owned by this tracer */
-        struct ds_context *context;
-        /* the buffer provided on ds_request() and its size in bytes */
-        void *buffer;
-        size_t size;
+        /* The DS context (partially) owned by this tracer. */
+        struct ds_context       *context;
+        /* The buffer provided on ds_request() and its size in bytes. */
+        void                    *buffer;
+        size_t                  size;
 };
 
 struct bts_tracer {
-        /* the common DS part */
-        struct ds_tracer ds;
-        /* the trace including the DS configuration */
-        struct bts_trace trace;
-        /* buffer overflow notification function */
-        bts_ovfl_callback_t ovfl;
+        /* The common DS part: */
+        struct ds_tracer        ds;
+
+        /* The trace including the DS configuration: */
+        struct bts_trace        trace;
+
+        /* Buffer overflow notification function: */
+        bts_ovfl_callback_t     ovfl;
+
+        /* Active flags affecting trace collection. */
+        unsigned int            flags;
 };
 
 struct pebs_tracer {
-        /* the common DS part */
-        struct ds_tracer ds;
-        /* the trace including the DS configuration */
-        struct pebs_trace trace;
-        /* buffer overflow notification function */
-        pebs_ovfl_callback_t ovfl;
+        /* The common DS part: */
+        struct ds_tracer        ds;
+
+        /* The trace including the DS configuration: */
+        struct pebs_trace       trace;
+
+        /* Buffer overflow notification function: */
+        pebs_ovfl_callback_t    ovfl;
 };
 
 /*
@@ -97,6 +120,7 @@ struct pebs_tracer {
  *
  * The DS configuration consists of the following fields; different
  * architetures vary in the size of those fields.
+ *
  * - double-word aligned base linear address of the BTS buffer
  * - write pointer into the BTS buffer
  * - end linear address of the BTS buffer (one byte beyond the end of
@@ -135,21 +159,22 @@ enum ds_field {
 };
 
 enum ds_qualifier {
-        ds_bts  = 0,
+        ds_bts = 0,
         ds_pebs
 };
 
-static inline unsigned long ds_get(const unsigned char *base,
-                                   enum ds_qualifier qual, enum ds_field field)
+static inline unsigned long
+ds_get(const unsigned char *base, enum ds_qualifier qual, enum ds_field field)
 {
-        base += (ds_cfg.sizeof_field * (field + (4 * qual)));
+        base += (ds_cfg.sizeof_ptr_field * (field + (4 * qual)));
         return *(unsigned long *)base;
 }
 
-static inline void ds_set(unsigned char *base, enum ds_qualifier qual,
-                          enum ds_field field, unsigned long value)
+static inline void
+ds_set(unsigned char *base, enum ds_qualifier qual, enum ds_field field,
+       unsigned long value)
 {
-        base += (ds_cfg.sizeof_field * (field + (4 * qual)));
+        base += (ds_cfg.sizeof_ptr_field * (field + (4 * qual)));
         (*(unsigned long *)base) = value;
 }
 
@@ -159,7 +184,6 @@ static inline void ds_set(unsigned char *base, enum ds_qualifier qual,
  */
 static DEFINE_SPINLOCK(ds_lock);
 
-
 /*
  * We either support (system-wide) per-cpu or per-thread allocation.
  * We distinguish the two based on the task_struct pointer, where a
@@ -178,12 +202,28 @@ static DEFINE_SPINLOCK(ds_lock);
  */
 static atomic_t tracers = ATOMIC_INIT(0);
 
-static inline void get_tracer(struct task_struct *task)
+static inline int get_tracer(struct task_struct *task)
 {
-        if (task)
+        int error;
+
+        spin_lock_irq(&ds_lock);
+
+        if (task) {
+                error = -EPERM;
+                if (atomic_read(&tracers) < 0)
+                        goto out;
                 atomic_inc(&tracers);
-        else
+        } else {
+                error = -EPERM;
+                if (atomic_read(&tracers) > 0)
+                        goto out;
                 atomic_dec(&tracers);
+        }
+
+        error = 0;
+out:
+        spin_unlock_irq(&ds_lock);
+        return error;
 }
 
 static inline void put_tracer(struct task_struct *task)
@@ -194,14 +234,6 @@ static inline void put_tracer(struct task_struct *task)
                 atomic_inc(&tracers);
 }
 
-static inline int check_tracer(struct task_struct *task)
-{
-        return task ?
-                (atomic_read(&tracers) >= 0) :
-                (atomic_read(&tracers) <= 0);
-}
-
-
 /*
  * The DS context is either attached to a thread or to a cpu:
  * - in the former case, the thread_struct contains a pointer to the
@@ -213,61 +245,58 @@ static inline int check_tracer(struct task_struct *task)
  * deallocated when the last user puts the context.
  */
 struct ds_context {
-        /* pointer to the DS configuration; goes into MSR_IA32_DS_AREA */
-        unsigned char ds[MAX_SIZEOF_DS];
-        /* the owner of the BTS and PEBS configuration, respectively */
-        struct bts_tracer *bts_master;
-        struct pebs_tracer *pebs_master;
-        /* use count */
-        unsigned long count;
-        /* a pointer to the context location inside the thread_struct
-         * or the per_cpu context array */
-        struct ds_context **this;
-        /* a pointer to the task owning this context, or NULL, if the
-         * context is owned by a cpu */
-        struct task_struct *task;
-};
+        /* The DS configuration; goes into MSR_IA32_DS_AREA: */
+        unsigned char           ds[MAX_SIZEOF_DS];
+
+        /* The owner of the BTS and PEBS configuration, respectively: */
+        struct bts_tracer       *bts_master;
+        struct pebs_tracer      *pebs_master;
 
-static DEFINE_PER_CPU(struct ds_context *, system_context_array);
+        /* Use count: */
+        unsigned long           count;
 
-#define system_context per_cpu(system_context_array, smp_processor_id())
+        /* Pointer to the context pointer field: */
+        struct ds_context       **this;
+
+        /* The traced task; NULL for cpu tracing: */
+        struct task_struct      *task;
+
+        /* The traced cpu; only valid if task is NULL: */
+        int                     cpu;
+};
 
+static DEFINE_PER_CPU(struct ds_context *, cpu_context);
 
-static inline struct ds_context *ds_get_context(struct task_struct *task)
+
+static struct ds_context *ds_get_context(struct task_struct *task, int cpu)
 {
         struct ds_context **p_context =
-                (task ? &task->thread.ds_ctx : &system_context);
+                (task ? &task->thread.ds_ctx : &per_cpu(cpu_context, cpu));
         struct ds_context *context = NULL;
         struct ds_context *new_context = NULL;
-        unsigned long irq;
 
         /* Chances are small that we already have a context. */
         new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
         if (!new_context)
                 return NULL;
 
-        spin_lock_irqsave(&ds_lock, irq);
+        spin_lock_irq(&ds_lock);
 
         context = *p_context;
-        if (!context) {
+        if (likely(!context)) {
                 context = new_context;
 
                 context->this = p_context;
                 context->task = task;
+                context->cpu = cpu;
                 context->count = 0;
 
-                if (task)
-                        set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
-
-                if (!task || (task == current))
-                        wrmsrl(MSR_IA32_DS_AREA, (unsigned long)context->ds);
-
                 *p_context = context;
         }
 
         context->count++;
 
-        spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irq(&ds_lock);
 
         if (context != new_context)
                 kfree(new_context);
@@ -275,8 +304,9 @@ static inline struct ds_context *ds_get_context(struct task_struct *task)
         return context;
 }
 
-static inline void ds_put_context(struct ds_context *context)
+static void ds_put_context(struct ds_context *context)
 {
+        struct task_struct *task;
         unsigned long irq;
 
         if (!context)
@@ -291,17 +321,55 @@ static inline void ds_put_context(struct ds_context *context)
 
         *(context->this) = NULL;
 
-        if (context->task)
-                clear_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);
+        task = context->task;
+
+        if (task)
+                clear_tsk_thread_flag(task, TIF_DS_AREA_MSR);
 
-        if (!context->task || (context->task == current))
-                wrmsrl(MSR_IA32_DS_AREA, 0);
+        /*
+         * We leave the (now dangling) pointer to the DS configuration in
+         * the DS_AREA msr. This is as good or as bad as replacing it with
+         * NULL - the hardware would crash if we enabled tracing.
+         *
+         * This saves us some problems with having to write an msr on a
+         * different cpu while preventing others from doing the same for the
+         * next context for that same cpu.
+         */
 
         spin_unlock_irqrestore(&ds_lock, irq);
 
+        /* The context might still be in use for context switching. */
+        if (task && (task != current))
+                wait_task_context_switch(task);
+
         kfree(context);
 }
 
+static void ds_install_ds_area(struct ds_context *context)
+{
+        unsigned long ds;
+
+        ds = (unsigned long)context->ds;
+
+        /*
+         * There is a race between the bts master and the pebs master.
+         *
+         * The thread/cpu access is synchronized via get/put_cpu() for
+         * task tracing and via wrmsr_on_cpu for cpu tracing.
+         *
+         * If bts and pebs are collected for the same task or same cpu,
+         * the same confiuration is written twice.
+         */
+        if (context->task) {
+                get_cpu();
+                if (context->task == current)
+                        wrmsrl(MSR_IA32_DS_AREA, ds);
+                set_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);
+                put_cpu();
+        } else
+                wrmsr_on_cpu(context->cpu, MSR_IA32_DS_AREA,
+                             (u32)((u64)ds), (u32)((u64)ds >> 32));
+}
 
 /*
  * Call the tracer's callback on a buffer overflow.
@@ -332,9 +400,9 @@ static void ds_overflow(struct ds_context *context, enum ds_qualifier qual)
  * The remainder of any partially written record is zeroed out.
  *
  * context: the DS context
- * qual: the buffer type
- * record: the data to write
- * size: the size of the data
+ * qual:    the buffer type
+ * record:  the data to write
+ * size:    the size of the data
  */
 static int ds_write(struct ds_context *context, enum ds_qualifier qual,
                     const void *record, size_t size)
@@ -349,14 +417,14 @@ static int ds_write(struct ds_context *context, enum ds_qualifier qual,
                 unsigned long write_size, adj_write_size;
 
                 /*
-                 * write as much as possible without producing an
+                 * Write as much as possible without producing an
                  * overflow interrupt.
                  *
-                 * interrupt_threshold must either be
+                 * Interrupt_threshold must either be
                  * - bigger than absolute_maximum or
                  * - point to a record between buffer_base and absolute_maximum
                  *
-                 * index points to a valid record.
+                 * Index points to a valid record.
                  */
                 base   = ds_get(context->ds, qual, ds_buffer_base);
                 index  = ds_get(context->ds, qual, ds_index);
@@ -365,8 +433,10 @@ static int ds_write(struct ds_context *context, enum ds_qualifier qual,
 
                 write_end = min(end, int_th);
 
-                /* if we are already beyond the interrupt threshold,
-                 * we fill the entire buffer */
+                /*
+                 * If we are already beyond the interrupt threshold,
+                 * we fill the entire buffer.
+                 */
                 if (write_end <= index)
                         write_end = end;
 
@@ -383,7 +453,7 @@ static int ds_write(struct ds_context *context, enum ds_qualifier qual,
                 adj_write_size = write_size / ds_cfg.sizeof_rec[qual];
                 adj_write_size *= ds_cfg.sizeof_rec[qual];
 
-                /* zero out trailing bytes */
+                /* Zero out trailing bytes. */
                 memset((char *)index + write_size, 0,
                        adj_write_size - write_size);
                 index += adj_write_size;
@@ -410,7 +480,7 @@ static int ds_write(struct ds_context *context, enum ds_qualifier qual,
  * Later architectures use 64bit pointers throughout, whereas earlier
  * architectures use 32bit pointers in 32bit mode.
  *
- * We compute the base address for the first 8 fields based on:
+ * We compute the base address for the fields based on:
  * - the field size stored in the DS configuration
  * - the relative field position
  *
@@ -431,23 +501,23 @@ enum bts_field {
         bts_to,
         bts_flags,
 
-        bts_qual = bts_from,
-        bts_jiffies = bts_to,
-        bts_pid = bts_flags,
+        bts_qual                = bts_from,
+        bts_clock               = bts_to,
+        bts_pid                 = bts_flags,
 
-        bts_qual_mask = (bts_qual_max - 1),
-        bts_escape = ((unsigned long)-1 & ~bts_qual_mask)
+        bts_qual_mask           = (bts_qual_max - 1),
+        bts_escape              = ((unsigned long)-1 & ~bts_qual_mask)
 };
 
 static inline unsigned long bts_get(const char *base, enum bts_field field)
 {
-        base += (ds_cfg.sizeof_field * field);
+        base += (ds_cfg.sizeof_ptr_field * field);
         return *(unsigned long *)base;
 }
 
 static inline void bts_set(char *base, enum bts_field field, unsigned long val)
 {
-        base += (ds_cfg.sizeof_field * field);;
+        base += (ds_cfg.sizeof_ptr_field * field);;
         (*(unsigned long *)base) = val;
 }
 
@@ -463,8 +533,8 @@ static inline void bts_set(char *base, enum bts_field field, unsigned long val)
  *
  * return: bytes read/written on success; -Eerrno, otherwise
  */
-static int bts_read(struct bts_tracer *tracer, const void *at,
-                    struct bts_struct *out)
+static int
+bts_read(struct bts_tracer *tracer, const void *at, struct bts_struct *out)
 {
         if (!tracer)
                 return -EINVAL;
@@ -478,8 +548,8 @@ static int bts_read(struct bts_tracer *tracer, const void *at,
         memset(out, 0, sizeof(*out));
         if ((bts_get(at, bts_qual) & ~bts_qual_mask) == bts_escape) {
                 out->qualifier = (bts_get(at, bts_qual) & bts_qual_mask);
-                out->variant.timestamp.jiffies = bts_get(at, bts_jiffies);
-                out->variant.timestamp.pid = bts_get(at, bts_pid);
+                out->variant.event.clock = bts_get(at, bts_clock);
+                out->variant.event.pid = bts_get(at, bts_pid);
         } else {
                 out->qualifier = bts_branch;
                 out->variant.lbr.from = bts_get(at, bts_from);
@@ -516,8 +586,8 @@ static int bts_write(struct bts_tracer *tracer, const struct bts_struct *in)
         case bts_task_arrives:
         case bts_task_departs:
                 bts_set(raw, bts_qual, (bts_escape | in->qualifier));
-                bts_set(raw, bts_jiffies, in->variant.timestamp.jiffies);
-                bts_set(raw, bts_pid, in->variant.timestamp.pid);
+                bts_set(raw, bts_clock, in->variant.event.clock);
+                bts_set(raw, bts_pid, in->variant.event.pid);
                 break;
         default:
                 return -EINVAL;
@@ -555,7 +625,8 @@ static void ds_init_ds_trace(struct ds_trace *trace, enum ds_qualifier qual,
                              unsigned int flags) {
         unsigned long buffer, adj;
 
-        /* adjust the buffer address and size to meet alignment
+        /*
+         * Adjust the buffer address and size to meet alignment
          * constraints:
          * - buffer is double-word aligned
          * - size is multiple of record size
@@ -577,9 +648,11 @@ static void ds_init_ds_trace(struct ds_trace *trace, enum ds_qualifier qual,
         trace->begin = (void *)buffer;
         trace->top = trace->begin;
         trace->end = (void *)(buffer + size);
-        /* The value for 'no threshold' is -1, which will set the
+        /*
+         * The value for 'no threshold' is -1, which will set the
          * threshold outside of the buffer, just like we want it.
          */
+        ith *= ds_cfg.sizeof_rec[qual];
         trace->ith = (void *)(buffer + size - ith);
 
         trace->flags = flags;
@@ -588,18 +661,27 @@ static void ds_init_ds_trace(struct ds_trace *trace, enum ds_qualifier qual,
 
 static int ds_request(struct ds_tracer *tracer, struct ds_trace *trace,
                       enum ds_qualifier qual, struct task_struct *task,
-                      void *base, size_t size, size_t th, unsigned int flags)
+                      int cpu, void *base, size_t size, size_t th)
 {
         struct ds_context *context;
         int error;
+        size_t req_size;
+
+        error = -EOPNOTSUPP;
+        if (!ds_cfg.sizeof_rec[qual])
+                goto out;
 
         error = -EINVAL;
         if (!base)
                 goto out;
 
-        /* we require some space to do alignment adjustments below */
+        req_size = ds_cfg.sizeof_rec[qual];
+        /* We might need space for alignment adjustments. */
+        if (!IS_ALIGNED((unsigned long)base, DS_ALIGNMENT))
+                req_size += DS_ALIGNMENT;
+
         error = -EINVAL;
-        if (size < (DS_ALIGNMENT + ds_cfg.sizeof_rec[qual]))
+        if (size < req_size)
                 goto out;
 
         if (th != (size_t)-1) {
@@ -614,182 +696,318 @@ static int ds_request(struct ds_tracer *tracer, struct ds_trace *trace,
         tracer->size = size;
 
         error = -ENOMEM;
-        context = ds_get_context(task);
+        context = ds_get_context(task, cpu);
         if (!context)
                 goto out;
         tracer->context = context;
 
-        ds_init_ds_trace(trace, qual, base, size, th, flags);
+        /*
+         * Defer any tracer-specific initialization work for the context until
+         * context ownership has been clarified.
+         */
 
         error = 0;
  out:
         return error;
 }
 
-struct bts_tracer *ds_request_bts(struct task_struct *task,
-                                  void *base, size_t size,
-                                  bts_ovfl_callback_t ovfl, size_t th,
-                                  unsigned int flags)
+static struct bts_tracer *ds_request_bts(struct task_struct *task, int cpu,
+                                         void *base, size_t size,
+                                         bts_ovfl_callback_t ovfl, size_t th,
+                                         unsigned int flags)
 {
         struct bts_tracer *tracer;
-        unsigned long irq;
         int error;
 
+        /* Buffer overflow notification is not yet implemented. */
         error = -EOPNOTSUPP;
-        if (!ds_cfg.ctl[dsf_bts])
+        if (ovfl)
                 goto out;
 
-        /* buffer overflow notification is not yet implemented */
-        error = -EOPNOTSUPP;
-        if (ovfl)
+        error = get_tracer(task);
+        if (error < 0)
                 goto out;
 
         error = -ENOMEM;
         tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
         if (!tracer)
-                goto out;
+                goto out_put_tracer;
         tracer->ovfl = ovfl;
 
+        /* Do some more error checking and acquire a tracing context. */
         error = ds_request(&tracer->ds, &tracer->trace.ds,
-                           ds_bts, task, base, size, th, flags);
+                           ds_bts, task, cpu, base, size, th);
         if (error < 0)
                 goto out_tracer;
 
-
-        spin_lock_irqsave(&ds_lock, irq);
-
-        error = -EPERM;
-        if (!check_tracer(task))
-                goto out_unlock;
-        get_tracer(task);
+        /* Claim the bts part of the tracing context we acquired above. */
+        spin_lock_irq(&ds_lock);
 
         error = -EPERM;
         if (tracer->ds.context->bts_master)
-                goto out_put_tracer;
+                goto out_unlock;
         tracer->ds.context->bts_master = tracer;
 
-        spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irq(&ds_lock);
 
+        /*
+         * Now that we own the bts part of the context, let's complete the
+         * initialization for that part.
+         */
+        ds_init_ds_trace(&tracer->trace.ds, ds_bts, base, size, th, flags);
+        ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
+        ds_install_ds_area(tracer->ds.context);
 
         tracer->trace.read  = bts_read;
         tracer->trace.write = bts_write;
 
-        ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
+        /* Start tracing. */
         ds_resume_bts(tracer);
 
         return tracer;
 
- out_put_tracer:
-        put_tracer(task);
  out_unlock:
-        spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irq(&ds_lock);
         ds_put_context(tracer->ds.context);
  out_tracer:
         kfree(tracer);
+ out_put_tracer:
+        put_tracer(task);
  out:
         return ERR_PTR(error);
 }
 
-struct pebs_tracer *ds_request_pebs(struct task_struct *task,
-                                    void *base, size_t size,
-                                    pebs_ovfl_callback_t ovfl, size_t th,
-                                    unsigned int flags)
+struct bts_tracer *ds_request_bts_task(struct task_struct *task,
+                                       void *base, size_t size,
+                                       bts_ovfl_callback_t ovfl,
+                                       size_t th, unsigned int flags)
+{
+        return ds_request_bts(task, 0, base, size, ovfl, th, flags);
+}
+
+struct bts_tracer *ds_request_bts_cpu(int cpu, void *base, size_t size,
+                                      bts_ovfl_callback_t ovfl,
+                                      size_t th, unsigned int flags)
+{
+        return ds_request_bts(NULL, cpu, base, size, ovfl, th, flags);
+}
+
+static struct pebs_tracer *ds_request_pebs(struct task_struct *task, int cpu,
+                                           void *base, size_t size,
+                                           pebs_ovfl_callback_t ovfl, size_t th,
+                                           unsigned int flags)
 {
         struct pebs_tracer *tracer;
-        unsigned long irq;
         int error;
 
-        /* buffer overflow notification is not yet implemented */
+        /* Buffer overflow notification is not yet implemented. */
         error = -EOPNOTSUPP;
         if (ovfl)
                 goto out;
 
+        error = get_tracer(task);
+        if (error < 0)
+                goto out;
+
         error = -ENOMEM;
         tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
         if (!tracer)
-                goto out;
+                goto out_put_tracer;
         tracer->ovfl = ovfl;
 
+        /* Do some more error checking and acquire a tracing context. */
         error = ds_request(&tracer->ds, &tracer->trace.ds,
-                           ds_pebs, task, base, size, th, flags);
+                           ds_pebs, task, cpu, base, size, th);
         if (error < 0)
                 goto out_tracer;
 
-        spin_lock_irqsave(&ds_lock, irq);
-
-        error = -EPERM;
-        if (!check_tracer(task))
-                goto out_unlock;
-        get_tracer(task);
+        /* Claim the pebs part of the tracing context we acquired above. */
+        spin_lock_irq(&ds_lock);
 
         error = -EPERM;
         if (tracer->ds.context->pebs_master)
-                goto out_put_tracer;
+                goto out_unlock;
         tracer->ds.context->pebs_master = tracer;
 
-        spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irq(&ds_lock);
 
+        /*
+         * Now that we own the pebs part of the context, let's complete the
+         * initialization for that part.
+         */
+        ds_init_ds_trace(&tracer->trace.ds, ds_pebs, base, size, th, flags);
         ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_pebs);
+        ds_install_ds_area(tracer->ds.context);
+
+        /* Start tracing. */
         ds_resume_pebs(tracer);
 
         return tracer;
 
- out_put_tracer:
-        put_tracer(task);
  out_unlock:
-        spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irq(&ds_lock);
         ds_put_context(tracer->ds.context);
  out_tracer:
         kfree(tracer);
+ out_put_tracer:
+        put_tracer(task);
  out:
         return ERR_PTR(error);
 }
 
-void ds_release_bts(struct bts_tracer *tracer)
+struct pebs_tracer *ds_request_pebs_task(struct task_struct *task,
+                                         void *base, size_t size,
+                                         pebs_ovfl_callback_t ovfl,
+                                         size_t th, unsigned int flags)
 {
-        if (!tracer)
-                return;
+        return ds_request_pebs(task, 0, base, size, ovfl, th, flags);
+}
 
-        ds_suspend_bts(tracer);
+struct pebs_tracer *ds_request_pebs_cpu(int cpu, void *base, size_t size,
+                                        pebs_ovfl_callback_t ovfl,
+                                        size_t th, unsigned int flags)
+{
+        return ds_request_pebs(NULL, cpu, base, size, ovfl, th, flags);
+}
+
+static void ds_free_bts(struct bts_tracer *tracer)
+{
+        struct task_struct *task;
+
+        task = tracer->ds.context->task;
 
         WARN_ON_ONCE(tracer->ds.context->bts_master != tracer);
         tracer->ds.context->bts_master = NULL;
 
-        put_tracer(tracer->ds.context->task);
+        /* Make sure tracing stopped and the tracer is not in use. */
+        if (task && (task != current))
+                wait_task_context_switch(task);
+
         ds_put_context(tracer->ds.context);
+        put_tracer(task);
 
         kfree(tracer);
 }
 
+void ds_release_bts(struct bts_tracer *tracer)
+{
+        might_sleep();
+
+        if (!tracer)
+                return;
+
+        ds_suspend_bts(tracer);
+        ds_free_bts(tracer);
+}
+
+int ds_release_bts_noirq(struct bts_tracer *tracer)
+{
+        struct task_struct *task;
+        unsigned long irq;
+        int error;
+
+        if (!tracer)
+                return 0;
+
+        task = tracer->ds.context->task;
+
+        local_irq_save(irq);
+
+        error = -EPERM;
+        if (!task &&
+            (tracer->ds.context->cpu != smp_processor_id()))
+                goto out;
+
+        error = -EPERM;
+        if (task && (task != current))
+                goto out;
+
+        ds_suspend_bts_noirq(tracer);
+        ds_free_bts(tracer);
+
+        error = 0;
+ out:
+        local_irq_restore(irq);
+        return error;
+}
+
+static void update_task_debugctlmsr(struct task_struct *task,
+                                    unsigned long debugctlmsr)
+{
+        task->thread.debugctlmsr = debugctlmsr;
+
+        get_cpu();
+        if (task == current)
+                update_debugctlmsr(debugctlmsr);
+        put_cpu();
+}
+
 void ds_suspend_bts(struct bts_tracer *tracer)
 {
         struct task_struct *task;
+        unsigned long debugctlmsr;
+        int cpu;
 
         if (!tracer)
                 return;
 
+        tracer->flags = 0;
+
         task = tracer->ds.context->task;
+        cpu  = tracer->ds.context->cpu;
 
-        if (!task || (task == current))
-                update_debugctlmsr(get_debugctlmsr() & ~BTS_CONTROL);
+        WARN_ON(!task && irqs_disabled());
 
-        if (task) {
-                task->thread.debugctlmsr &= ~BTS_CONTROL;
+        debugctlmsr = (task ?
+                       task->thread.debugctlmsr :
+                       get_debugctlmsr_on_cpu(cpu));
+        debugctlmsr &= ~BTS_CONTROL;
 
-                if (!task->thread.debugctlmsr)
-                        clear_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
-        }
+        if (task)
+                update_task_debugctlmsr(task, debugctlmsr);
+        else
+                update_debugctlmsr_on_cpu(cpu, debugctlmsr);
 }
 
-void ds_resume_bts(struct bts_tracer *tracer)
+int ds_suspend_bts_noirq(struct bts_tracer *tracer)
 {
         struct task_struct *task;
-        unsigned long control;
+        unsigned long debugctlmsr, irq;
+        int cpu, error = 0;
 
         if (!tracer)
-                return;
+                return 0;
+
+        tracer->flags = 0;
 
         task = tracer->ds.context->task;
+        cpu  = tracer->ds.context->cpu;
+
+        local_irq_save(irq);
+
+        error = -EPERM;
+        if (!task && (cpu != smp_processor_id()))
+                goto out;
+
+        debugctlmsr = (task ?
+                       task->thread.debugctlmsr :
+                       get_debugctlmsr());
+        debugctlmsr &= ~BTS_CONTROL;
+
+        if (task)
+                update_task_debugctlmsr(task, debugctlmsr);
+        else
+                update_debugctlmsr(debugctlmsr);
+
+        error = 0;
+ out:
+        local_irq_restore(irq);
+        return error;
+}
+
+static unsigned long ds_bts_control(struct bts_tracer *tracer)
+{
+        unsigned long control;
 
         control = ds_cfg.ctl[dsf_bts];
         if (!(tracer->trace.ds.flags & BTS_KERNEL))
@@ -797,41 +1015,149 @@ void ds_resume_bts(struct bts_tracer *tracer)
         if (!(tracer->trace.ds.flags & BTS_USER))
                 control |= ds_cfg.ctl[dsf_bts_user];
 
-        if (task) {
-                task->thread.debugctlmsr |= control;
-                set_tsk_thread_flag(task, TIF_DEBUGCTLMSR);
-        }
-
-        if (!task || (task == current))
-                update_debugctlmsr(get_debugctlmsr() | control);
+        return control;
 }
 
-void ds_release_pebs(struct pebs_tracer *tracer)
+void ds_resume_bts(struct bts_tracer *tracer)
 {
+        struct task_struct *task;
+        unsigned long debugctlmsr;
+        int cpu;
+
         if (!tracer)
                 return;
 
-        ds_suspend_pebs(tracer);
+        tracer->flags = tracer->trace.ds.flags;
+
+        task = tracer->ds.context->task;
+        cpu  = tracer->ds.context->cpu;
+
+        WARN_ON(!task && irqs_disabled());
+
+        debugctlmsr = (task ?
+                       task->thread.debugctlmsr :
+                       get_debugctlmsr_on_cpu(cpu));
+        debugctlmsr |= ds_bts_control(tracer);
+
+        if (task)
+                update_task_debugctlmsr(task, debugctlmsr);
+        else
+                update_debugctlmsr_on_cpu(cpu, debugctlmsr);
+}
+
+int ds_resume_bts_noirq(struct bts_tracer *tracer)
+{
+        struct task_struct *task;
+        unsigned long debugctlmsr, irq;
+        int cpu, error = 0;
+
+        if (!tracer)
+                return 0;
+
+        tracer->flags = tracer->trace.ds.flags;
+
+        task = tracer->ds.context->task;
+        cpu  = tracer->ds.context->cpu;
+
+        local_irq_save(irq);
+
+        error = -EPERM;
+        if (!task && (cpu != smp_processor_id()))
+                goto out;
+
+        debugctlmsr = (task ?
+                       task->thread.debugctlmsr :
+                       get_debugctlmsr());
+        debugctlmsr |= ds_bts_control(tracer);
+
+        if (task)
+                update_task_debugctlmsr(task, debugctlmsr);
+        else
+                update_debugctlmsr(debugctlmsr);
+
+        error = 0;
+ out:
+        local_irq_restore(irq);
+        return error;
+}
+
+static void ds_free_pebs(struct pebs_tracer *tracer)
+{
+        struct task_struct *task;
+
+        task = tracer->ds.context->task;
 
         WARN_ON_ONCE(tracer->ds.context->pebs_master != tracer);
         tracer->ds.context->pebs_master = NULL;
 
-        put_tracer(tracer->ds.context->task);
         ds_put_context(tracer->ds.context);
+        put_tracer(task);
 
         kfree(tracer);
 }
 
+void ds_release_pebs(struct pebs_tracer *tracer)
+{
+        might_sleep();
+
+        if (!tracer)
+                return;
+
+        ds_suspend_pebs(tracer);
+        ds_free_pebs(tracer);
+}
+
+int ds_release_pebs_noirq(struct pebs_tracer *tracer)
+{
+        struct task_struct *task;
+        unsigned long irq;
+        int error;
+
+        if (!tracer)
+                return 0;
+
+        task = tracer->ds.context->task;
+
+        local_irq_save(irq);
+
+        error = -EPERM;
+        if (!task &&
+            (tracer->ds.context->cpu != smp_processor_id()))
+                goto out;
+
+        error = -EPERM;
+        if (task && (task != current))
+                goto out;
+
+        ds_suspend_pebs_noirq(tracer);
+        ds_free_pebs(tracer);
+
+        error = 0;
+ out:
+        local_irq_restore(irq);
+        return error;
+}
+
 void ds_suspend_pebs(struct pebs_tracer *tracer)
 {
 
 }
 
+int ds_suspend_pebs_noirq(struct pebs_tracer *tracer)
+{
+        return 0;
+}
+
 void ds_resume_pebs(struct pebs_tracer *tracer)
 {
 
 }
 
+int ds_resume_pebs_noirq(struct pebs_tracer *tracer)
+{
+        return 0;
+}
+
 const struct bts_trace *ds_read_bts(struct bts_tracer *tracer)
 {
         if (!tracer)
@@ -847,8 +1173,12 @@ const struct pebs_trace *ds_read_pebs(struct pebs_tracer *tracer)
                 return NULL;
 
         ds_read_config(tracer->ds.context, &tracer->trace.ds, ds_pebs);
-        tracer->trace.reset_value =
-                *(u64 *)(tracer->ds.context->ds + (ds_cfg.sizeof_field * 8));
+
+        tracer->trace.counters = ds_cfg.nr_counter_reset;
+        memcpy(tracer->trace.counter_reset,
+               tracer->ds.context->ds +
+               (NUM_DS_PTR_FIELDS * ds_cfg.sizeof_ptr_field),
+               ds_cfg.nr_counter_reset * PEBS_RESET_FIELD_SIZE);
 
         return &tracer->trace;
 }
@@ -873,18 +1203,24 @@ int ds_reset_pebs(struct pebs_tracer *tracer)
 
         tracer->trace.ds.top = tracer->trace.ds.begin;
 
-        ds_set(tracer->ds.context->ds, ds_bts, ds_index,
+        ds_set(tracer->ds.context->ds, ds_pebs, ds_index,
                (unsigned long)tracer->trace.ds.top);
 
         return 0;
 }
 
-int ds_set_pebs_reset(struct pebs_tracer *tracer, u64 value)
+int ds_set_pebs_reset(struct pebs_tracer *tracer,
+                      unsigned int counter, u64 value)
 {
         if (!tracer)
                 return -EINVAL;
 
-        *(u64 *)(tracer->ds.context->ds + (ds_cfg.sizeof_field * 8)) = value;
+        if (ds_cfg.nr_counter_reset < counter)
+                return -EINVAL;
+
+        *(u64 *)(tracer->ds.context->ds +
+                 (NUM_DS_PTR_FIELDS * ds_cfg.sizeof_ptr_field) +
+                 (counter * PEBS_RESET_FIELD_SIZE)) = value;
 
         return 0;
 }
@@ -894,73 +1230,117 @@ static const struct ds_configuration ds_cfg_netburst = {
         .ctl[dsf_bts]           = (1 << 2) | (1 << 3),
         .ctl[dsf_bts_kernel]    = (1 << 5),
         .ctl[dsf_bts_user]      = (1 << 6),
-
-        .sizeof_field           = sizeof(long),
-        .sizeof_rec[ds_bts]     = sizeof(long) * 3,
-#ifdef __i386__
-        .sizeof_rec[ds_pebs]    = sizeof(long) * 10,
-#else
-        .sizeof_rec[ds_pebs]    = sizeof(long) * 18,
-#endif
+        .nr_counter_reset       = 1,
 };
 static const struct ds_configuration ds_cfg_pentium_m = {
         .name = "Pentium M",
         .ctl[dsf_bts]           = (1 << 6) | (1 << 7),
-
-        .sizeof_field           = sizeof(long),
-        .sizeof_rec[ds_bts]     = sizeof(long) * 3,
-#ifdef __i386__
-        .sizeof_rec[ds_pebs]    = sizeof(long) * 10,
-#else
-        .sizeof_rec[ds_pebs]    = sizeof(long) * 18,
-#endif
+        .nr_counter_reset       = 1,
 };
 static const struct ds_configuration ds_cfg_core2_atom = {
         .name = "Core 2/Atom",
         .ctl[dsf_bts]           = (1 << 6) | (1 << 7),
         .ctl[dsf_bts_kernel]    = (1 << 9),
         .ctl[dsf_bts_user]      = (1 << 10),
-
-        .sizeof_field           = 8,
-        .sizeof_rec[ds_bts]     = 8 * 3,
-        .sizeof_rec[ds_pebs]    = 8 * 18,
+        .nr_counter_reset       = 1,
+};
+static const struct ds_configuration ds_cfg_core_i7 = {
+        .name = "Core i7",
+        .ctl[dsf_bts]           = (1 << 6) | (1 << 7),
+        .ctl[dsf_bts_kernel]    = (1 << 9),
+        .ctl[dsf_bts_user]      = (1 << 10),
+        .nr_counter_reset       = 4,
 };
 
 static void
-ds_configure(const struct ds_configuration *cfg)
+ds_configure(const struct ds_configuration *cfg,
+             struct cpuinfo_x86 *cpu)
 {
+        unsigned long nr_pebs_fields = 0;
+
+        printk(KERN_INFO "[ds] using %s configuration\n", cfg->name);
+
+#ifdef __i386__
+        nr_pebs_fields = 10;
+#else
+        nr_pebs_fields = 18;
+#endif
+
+        /*
+         * Starting with version 2, architectural performance
+         * monitoring supports a format specifier.
+         */
+        if ((cpuid_eax(0xa) & 0xff) > 1) {
+                unsigned long perf_capabilities, format;
+
+                rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_capabilities);
+
+                format = (perf_capabilities >> 8) & 0xf;
+
+                switch (format) {
+                case 0:
+                        nr_pebs_fields = 18;
+                        break;
+                case 1:
+                        nr_pebs_fields = 22;
+                        break;
+                default:
+                        printk(KERN_INFO
+                               "[ds] unknown PEBS format: %lu\n", format);
+                        nr_pebs_fields = 0;
+                        break;
+                }
+        }
+
         memset(&ds_cfg, 0, sizeof(ds_cfg));
         ds_cfg = *cfg;
 
-        printk(KERN_INFO "[ds] using %s configuration\n", ds_cfg.name);
+        ds_cfg.sizeof_ptr_field =
+                (cpu_has(cpu, X86_FEATURE_DTES64) ? 8 : 4);
+
+        ds_cfg.sizeof_rec[ds_bts]  = ds_cfg.sizeof_ptr_field * 3;
+        ds_cfg.sizeof_rec[ds_pebs] = ds_cfg.sizeof_ptr_field * nr_pebs_fields;
 
-        if (!cpu_has_bts) {
-                ds_cfg.ctl[dsf_bts] = 0;
+        if (!cpu_has(cpu, X86_FEATURE_BTS)) {
+                ds_cfg.sizeof_rec[ds_bts] = 0;
                 printk(KERN_INFO "[ds] bts not available\n");
         }
-        if (!cpu_has_pebs)
+        if (!cpu_has(cpu, X86_FEATURE_PEBS)) {
+                ds_cfg.sizeof_rec[ds_pebs] = 0;
                 printk(KERN_INFO "[ds] pebs not available\n");
+        }
+
+        printk(KERN_INFO "[ds] sizes: address: %u bit, ",
+               8 * ds_cfg.sizeof_ptr_field);
+        printk("bts/pebs record: %u/%u bytes\n",
+               ds_cfg.sizeof_rec[ds_bts], ds_cfg.sizeof_rec[ds_pebs]);
 
-        WARN_ON_ONCE(MAX_SIZEOF_DS < (12 * ds_cfg.sizeof_field));
+        WARN_ON_ONCE(MAX_PEBS_COUNTERS < ds_cfg.nr_counter_reset);
 }
 
 void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
 {
+        /* Only configure the first cpu. Others are identical. */
+        if (ds_cfg.name)
+                return;
+
         switch (c->x86) {
         case 0x6:
                 switch (c->x86_model) {
                 case 0x9:
                 case 0xd: /* Pentium M */
-                        ds_configure(&ds_cfg_pentium_m);
+                        ds_configure(&ds_cfg_pentium_m, c);
                         break;
                 case 0xf:
                 case 0x17: /* Core2 */
                 case 0x1c: /* Atom */
-                        ds_configure(&ds_cfg_core2_atom);
+                        ds_configure(&ds_cfg_core2_atom, c);
+                        break;
+                case 0x1a: /* Core i7 */
+                        ds_configure(&ds_cfg_core_i7, c);
                         break;
-                case 0x1a: /* i7 */
                 default:
-                        /* sorry, don't know about them */
+                        /* Sorry, don't know about them. */
                         break;
                 }
                 break;
@@ -969,64 +1349,89 @@ void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
                 case 0x0:
                 case 0x1:
                 case 0x2: /* Netburst */
-                        ds_configure(&ds_cfg_netburst);
+                        ds_configure(&ds_cfg_netburst, c);
                         break;
                 default:
-                        /* sorry, don't know about them */
+                        /* Sorry, don't know about them. */
                         break;
                 }
                 break;
         default:
-                /* sorry, don't know about them */
+                /* Sorry, don't know about them. */
                 break;
         }
 }
 
+static inline void ds_take_timestamp(struct ds_context *context,
+                                     enum bts_qualifier qualifier,
+                                     struct task_struct *task)
+{
+        struct bts_tracer *tracer = context->bts_master;
+        struct bts_struct ts;
+
+        /* Prevent compilers from reading the tracer pointer twice. */
+        barrier();
+
+        if (!tracer || !(tracer->flags & BTS_TIMESTAMPS))
+                return;
+
+        memset(&ts, 0, sizeof(ts));
+        ts.qualifier            = qualifier;
+        ts.variant.event.clock  = trace_clock_global();
+        ts.variant.event.pid    = task->pid;
+
+        bts_write(tracer, &ts);
+}
+
 /*
  * Change the DS configuration from tracing prev to tracing next.
  */
 void ds_switch_to(struct task_struct *prev, struct task_struct *next)
 {
-        struct ds_context *prev_ctx = prev->thread.ds_ctx;
-        struct ds_context *next_ctx = next->thread.ds_ctx;
+        struct ds_context *prev_ctx     = prev->thread.ds_ctx;
+        struct ds_context *next_ctx     = next->thread.ds_ctx;
+        unsigned long debugctlmsr       = next->thread.debugctlmsr;
+
+        /* Make sure all data is read before we start. */
+        barrier();
 
         if (prev_ctx) {
                 update_debugctlmsr(0);
 
-                if (prev_ctx->bts_master &&
-                    (prev_ctx->bts_master->trace.ds.flags & BTS_TIMESTAMPS)) {
-                        struct bts_struct ts = {
-                                .qualifier = bts_task_departs,
-                                .variant.timestamp.jiffies = jiffies_64,
-                                .variant.timestamp.pid = prev->pid
-                        };
-                        bts_write(prev_ctx->bts_master, &ts);
-                }
+                ds_take_timestamp(prev_ctx, bts_task_departs, prev);
         }
 
         if (next_ctx) {
-                if (next_ctx->bts_master &&
-                    (next_ctx->bts_master->trace.ds.flags & BTS_TIMESTAMPS)) {
-                        struct bts_struct ts = {
-                                .qualifier = bts_task_arrives,
-                                .variant.timestamp.jiffies = jiffies_64,
-                                .variant.timestamp.pid = next->pid
-                        };
-                        bts_write(next_ctx->bts_master, &ts);
-                }
+                ds_take_timestamp(next_ctx, bts_task_arrives, next);
 
                 wrmsrl(MSR_IA32_DS_AREA, (unsigned long)next_ctx->ds);
         }
 
-        update_debugctlmsr(next->thread.debugctlmsr);
+        update_debugctlmsr(debugctlmsr);
 }
 
-void ds_copy_thread(struct task_struct *tsk, struct task_struct *father)
+static __init int ds_selftest(void)
 {
-        clear_tsk_thread_flag(tsk, TIF_DS_AREA_MSR);
-        tsk->thread.ds_ctx = NULL;
-}
+        if (ds_cfg.sizeof_rec[ds_bts]) {
+                int error;
 
-void ds_exit_thread(struct task_struct *tsk)
-{
+                error = ds_selftest_bts();
+                if (error) {
+                        WARN(1, "[ds] selftest failed. disabling bts.\n");
+                        ds_cfg.sizeof_rec[ds_bts] = 0;
+                }
+        }
+
+        if (ds_cfg.sizeof_rec[ds_pebs]) {
+                int error;
+
+                error = ds_selftest_pebs();
+                if (error) {
+                        WARN(1, "[ds] selftest failed. disabling pebs.\n");
+                        ds_cfg.sizeof_rec[ds_pebs] = 0;
+                }
+        }
+
+        return 0;
 }
+device_initcall(ds_selftest);