virt/kvm/kvm_trace.c

   1 /*
   2  * kvm trace
   3  *
   4  * It is designed to allow debugging traces of kvm to be generated
   5  * on UP / SMP machines.  Each trace entry can be timestamped so that
   6  * it's possible to reconstruct a chronological record of trace events.
   7  * The implementation refers to blktrace kernel support.
   8  *
   9  * Copyright (c) 2008 Intel Corporation
  10  * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
  11  *
  12  * Authors: Feng(Eric) Liu, eric.e.liu@intel.com
  13  *
  14  * Date:    Feb 2008
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/relay.h>
  19 #include <linux/debugfs.h>
  20
  21 #include <linux/kvm_host.h>
  22
  23 #define KVM_TRACE_STATE_RUNNING         (1 << 0)
  24 #define KVM_TRACE_STATE_PAUSE           (1 << 1)
  25 #define KVM_TRACE_STATE_CLEARUP         (1 << 2)
  26
  27 struct kvm_trace {
  28         int trace_state;
  29         struct rchan *rchan;
  30         struct dentry *lost_file;
  31         atomic_t lost_records;
  32 };
  33 static struct kvm_trace *kvm_trace;
  34
  35 struct kvm_trace_probe {
  36         const char *name;
  37         const char *format;
  38         u32 cycle_in;
  39         marker_probe_func *probe_func;
  40 };
  41
  42 static inline int calc_rec_size(int cycle, int extra)
  43 {
  44         int rec_size = KVM_TRC_HEAD_SIZE;
  45
  46         rec_size += extra;
  47         return cycle ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
  48 }
  49
  50 static void kvm_add_trace(void *probe_private, void *call_data,
  51                           const char *format, va_list *args)
  52 {
  53         struct kvm_trace_probe *p = probe_private;
  54         struct kvm_trace *kt = kvm_trace;
  55         struct kvm_trace_rec rec;
  56         struct kvm_vcpu *vcpu;
  57         int    i, extra, size;
  58
  59         if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
  60                 return;
  61
  62         rec.event       = va_arg(*args, u32);
  63         vcpu            = va_arg(*args, struct kvm_vcpu *);
  64         rec.pid         = current->tgid;
  65         rec.vcpu_id     = vcpu->vcpu_id;
  66
  67         extra           = va_arg(*args, u32);
  68         WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
  69         extra           = min_t(u32, extra, KVM_TRC_EXTRA_MAX);
  70         rec.extra_u32   = extra;
  71
  72         rec.cycle_in    = p->cycle_in;
  73
  74         if (rec.cycle_in) {
  75                 u64 cycle = 0;
  76
  77                 cycle = get_cycles();
  78                 rec.u.cycle.cycle_lo = (u32)cycle;
  79                 rec.u.cycle.cycle_hi = (u32)(cycle >> 32);
  80
  81                 for (i = 0; i < rec.extra_u32; i++)
  82                         rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
  83         } else {
  84                 for (i = 0; i < rec.extra_u32; i++)
  85                         rec.u.nocycle.extra_u32[i] = va_arg(*args, u32);
  86         }
  87
  88         size = calc_rec_size(rec.cycle_in, rec.extra_u32 * sizeof(u32));
  89         relay_write(kt->rchan, &rec, size);
  90 }
  91
  92 static struct kvm_trace_probe kvm_trace_probes[] = {
  93         { "kvm_trace_entryexit", "%u %p %u %u %u %u %u %u", 1, kvm_add_trace },
  94         { "kvm_trace_handler", "%u %p %u %u %u %u %u %u", 0, kvm_add_trace },
  95 };
  96
  97 static int lost_records_get(void *data, u64 *val)
  98 {
  99         struct kvm_trace *kt = data;
 100
 101         *val = atomic_read(&kt->lost_records);
 102         return 0;
 103 }
 104
 105 DEFINE_SIMPLE_ATTRIBUTE(kvm_trace_lost_ops, lost_records_get, NULL, "%llu\n");
 106
 107 /*
 108  *  The relay channel is used in "no-overwrite" mode, it keeps trace of how
 109  *  many times we encountered a full subbuffer, to tell user space app the
 110  *  lost records there were.
 111  */
 112 static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 113                                      void *prev_subbuf, size_t prev_padding)
 114 {
 115         struct kvm_trace *kt;
 116
 117         if (!relay_buf_full(buf))
 118                 return 1;
 119
 120         kt = buf->chan->private_data;
 121         atomic_inc(&kt->lost_records);
 122
 123         return 0;
 124 }
 125
 126 static struct dentry *kvm_create_buf_file_callack(const char *filename,
 127                                                  struct dentry *parent,
 128                                                  int mode,
 129                                                  struct rchan_buf *buf,
 130                                                  int *is_global)
 131 {
 132         return debugfs_create_file(filename, mode, parent, buf,
 133                                    &relay_file_operations);
 134 }
 135
 136 static int kvm_remove_buf_file_callback(struct dentry *dentry)
 137 {
 138         debugfs_remove(dentry);
 139         return 0;
 140 }
 141
 142 static struct rchan_callbacks kvm_relay_callbacks = {
 143         .subbuf_start           = kvm_subbuf_start_callback,
 144         .create_buf_file        = kvm_create_buf_file_callack,
 145         .remove_buf_file        = kvm_remove_buf_file_callback,
 146 };
 147
 148 static int do_kvm_trace_enable(struct kvm_user_trace_setup *kuts)
 149 {
 150         struct kvm_trace *kt;
 151         int i, r = -ENOMEM;
 152
 153         if (!kuts->buf_size || !kuts->buf_nr)
 154                 return -EINVAL;
 155
 156         kt = kzalloc(sizeof(*kt), GFP_KERNEL);
 157         if (!kt)
 158                 goto err;
 159
 160         r = -EIO;
 161         atomic_set(&kt->lost_records, 0);
 162         kt->lost_file = debugfs_create_file("lost_records", 0444, kvm_debugfs_dir,
 163                                             kt, &kvm_trace_lost_ops);
 164         if (!kt->lost_file)
 165                 goto err;
 166
 167         kt->rchan = relay_open("trace", kvm_debugfs_dir, kuts->buf_size,
 168                                 kuts->buf_nr, &kvm_relay_callbacks, kt);
 169         if (!kt->rchan)
 170                 goto err;
 171
 172         kvm_trace = kt;
 173
 174         for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 175                 struct kvm_trace_probe *p = &kvm_trace_probes[i];
 176
 177                 r = marker_probe_register(p->name, p->format, p->probe_func, p);
 178                 if (r)
 179                         printk(KERN_INFO "Unable to register probe %s\n",
 180                                p->name);
 181         }
 182
 183         kvm_trace->trace_state = KVM_TRACE_STATE_RUNNING;
 184
 185         return 0;
 186 err:
 187         if (kt) {
 188                 if (kt->lost_file)
 189                         debugfs_remove(kt->lost_file);
 190                 if (kt->rchan)
 191                         relay_close(kt->rchan);
 192                 kfree(kt);
 193         }
 194         return r;
 195 }
 196
 197 static int kvm_trace_enable(char __user *arg)
 198 {
 199         struct kvm_user_trace_setup kuts;
 200         int ret;
 201
 202         ret = copy_from_user(&kuts, arg, sizeof(kuts));
 203         if (ret)
 204                 return -EFAULT;
 205
 206         ret = do_kvm_trace_enable(&kuts);
 207         if (ret)
 208                 return ret;
 209
 210         return 0;
 211 }
 212
 213 static int kvm_trace_pause(void)
 214 {
 215         struct kvm_trace *kt = kvm_trace;
 216         int r = -EINVAL;
 217
 218         if (kt == NULL)
 219                 return r;
 220
 221         if (kt->trace_state == KVM_TRACE_STATE_RUNNING) {
 222                 kt->trace_state = KVM_TRACE_STATE_PAUSE;
 223                 relay_flush(kt->rchan);
 224                 r = 0;
 225         }
 226
 227         return r;
 228 }
 229
 230 void kvm_trace_cleanup(void)
 231 {
 232         struct kvm_trace *kt = kvm_trace;
 233         int i;
 234
 235         if (kt == NULL)
 236                 return;
 237
 238         if (kt->trace_state == KVM_TRACE_STATE_RUNNING ||
 239             kt->trace_state == KVM_TRACE_STATE_PAUSE) {
 240
 241                 kt->trace_state = KVM_TRACE_STATE_CLEARUP;
 242
 243                 for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 244                         struct kvm_trace_probe *p = &kvm_trace_probes[i];
 245                         marker_probe_unregister(p->name, p->probe_func, p);
 246                 }
 247
 248                 relay_close(kt->rchan);
 249                 debugfs_remove(kt->lost_file);
 250                 kfree(kt);
 251         }
 252 }
 253
 254 int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
 255 {
 256         void __user *argp = (void __user *)arg;
 257         long r = -EINVAL;
 258
 259         if (!capable(CAP_SYS_ADMIN))
 260                 return -EPERM;
 261
 262         switch (ioctl) {
 263         case KVM_TRACE_ENABLE:
 264                 r = kvm_trace_enable(argp);
 265                 break;
 266         case KVM_TRACE_PAUSE:
 267                 r = kvm_trace_pause();
 268                 break;
 269         case KVM_TRACE_DISABLE:
 270                 r = 0;
 271                 kvm_trace_cleanup();
 272                 break;
 273         }
 274
 275         return r;
 276 }