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                 rec.u.cycle.cycle_u64 = get_cycles();
  76
  77                 for (i = 0; i < rec.extra_u32; i++)
  78                         rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
  79         } else {
  80                 for (i = 0; i < rec.extra_u32; i++)
  81                         rec.u.nocycle.extra_u32[i] = va_arg(*args, u32);
  82         }
  83
  84         size = calc_rec_size(rec.cycle_in, rec.extra_u32 * sizeof(u32));
  85         relay_write(kt->rchan, &rec, size);
  86 }
  87
  88 static struct kvm_trace_probe kvm_trace_probes[] = {
  89         { "kvm_trace_entryexit", "%u %p %u %u %u %u %u %u", 1, kvm_add_trace },
  90         { "kvm_trace_handler", "%u %p %u %u %u %u %u %u", 0, kvm_add_trace },
  91 };
  92
  93 static int lost_records_get(void *data, u64 *val)
  94 {
  95         struct kvm_trace *kt = data;
  96
  97         *val = atomic_read(&kt->lost_records);
  98         return 0;
  99 }
 100
 101 DEFINE_SIMPLE_ATTRIBUTE(kvm_trace_lost_ops, lost_records_get, NULL, "%llu\n");
 102
 103 /*
 104  *  The relay channel is used in "no-overwrite" mode, it keeps trace of how
 105  *  many times we encountered a full subbuffer, to tell user space app the
 106  *  lost records there were.
 107  */
 108 static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 109                                      void *prev_subbuf, size_t prev_padding)
 110 {
 111         struct kvm_trace *kt;
 112
 113         if (!relay_buf_full(buf)) {
 114                 if (!prev_subbuf) {
 115                         /*
 116                          * executed only once when the channel is opened
 117                          * save metadata as first record
 118                          */
 119                         subbuf_start_reserve(buf, sizeof(u32));
 120                         *(u32 *)subbuf = 0x12345678;
 121                 }
 122
 123                 return 1;
 124         }
 125
 126         kt = buf->chan->private_data;
 127         atomic_inc(&kt->lost_records);
 128
 129         return 0;
 130 }
 131
 132 static struct dentry *kvm_create_buf_file_callack(const char *filename,
 133                                                  struct dentry *parent,
 134                                                  int mode,
 135                                                  struct rchan_buf *buf,
 136                                                  int *is_global)
 137 {
 138         return debugfs_create_file(filename, mode, parent, buf,
 139                                    &relay_file_operations);
 140 }
 141
 142 static int kvm_remove_buf_file_callback(struct dentry *dentry)
 143 {
 144         debugfs_remove(dentry);
 145         return 0;
 146 }
 147
 148 static struct rchan_callbacks kvm_relay_callbacks = {
 149         .subbuf_start           = kvm_subbuf_start_callback,
 150         .create_buf_file        = kvm_create_buf_file_callack,
 151         .remove_buf_file        = kvm_remove_buf_file_callback,
 152 };
 153
 154 static int do_kvm_trace_enable(struct kvm_user_trace_setup *kuts)
 155 {
 156         struct kvm_trace *kt;
 157         int i, r = -ENOMEM;
 158
 159         if (!kuts->buf_size || !kuts->buf_nr)
 160                 return -EINVAL;
 161
 162         kt = kzalloc(sizeof(*kt), GFP_KERNEL);
 163         if (!kt)
 164                 goto err;
 165
 166         r = -EIO;
 167         atomic_set(&kt->lost_records, 0);
 168         kt->lost_file = debugfs_create_file("lost_records", 0444, kvm_debugfs_dir,
 169                                             kt, &kvm_trace_lost_ops);
 170         if (!kt->lost_file)
 171                 goto err;
 172
 173         kt->rchan = relay_open("trace", kvm_debugfs_dir, kuts->buf_size,
 174                                 kuts->buf_nr, &kvm_relay_callbacks, kt);
 175         if (!kt->rchan)
 176                 goto err;
 177
 178         kvm_trace = kt;
 179
 180         for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 181                 struct kvm_trace_probe *p = &kvm_trace_probes[i];
 182
 183                 r = marker_probe_register(p->name, p->format, p->probe_func, p);
 184                 if (r)
 185                         printk(KERN_INFO "Unable to register probe %s\n",
 186                                p->name);
 187         }
 188
 189         kvm_trace->trace_state = KVM_TRACE_STATE_RUNNING;
 190
 191         return 0;
 192 err:
 193         if (kt) {
 194                 if (kt->lost_file)
 195                         debugfs_remove(kt->lost_file);
 196                 if (kt->rchan)
 197                         relay_close(kt->rchan);
 198                 kfree(kt);
 199         }
 200         return r;
 201 }
 202
 203 static int kvm_trace_enable(char __user *arg)
 204 {
 205         struct kvm_user_trace_setup kuts;
 206         int ret;
 207
 208         ret = copy_from_user(&kuts, arg, sizeof(kuts));
 209         if (ret)
 210                 return -EFAULT;
 211
 212         ret = do_kvm_trace_enable(&kuts);
 213         if (ret)
 214                 return ret;
 215
 216         return 0;
 217 }
 218
 219 static int kvm_trace_pause(void)
 220 {
 221         struct kvm_trace *kt = kvm_trace;
 222         int r = -EINVAL;
 223
 224         if (kt == NULL)
 225                 return r;
 226
 227         if (kt->trace_state == KVM_TRACE_STATE_RUNNING) {
 228                 kt->trace_state = KVM_TRACE_STATE_PAUSE;
 229                 relay_flush(kt->rchan);
 230                 r = 0;
 231         }
 232
 233         return r;
 234 }
 235
 236 void kvm_trace_cleanup(void)
 237 {
 238         struct kvm_trace *kt = kvm_trace;
 239         int i;
 240
 241         if (kt == NULL)
 242                 return;
 243
 244         if (kt->trace_state == KVM_TRACE_STATE_RUNNING ||
 245             kt->trace_state == KVM_TRACE_STATE_PAUSE) {
 246
 247                 kt->trace_state = KVM_TRACE_STATE_CLEARUP;
 248
 249                 for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 250                         struct kvm_trace_probe *p = &kvm_trace_probes[i];
 251                         marker_probe_unregister(p->name, p->probe_func, p);
 252                 }
 253
 254                 relay_close(kt->rchan);
 255                 debugfs_remove(kt->lost_file);
 256                 kfree(kt);
 257         }
 258 }
 259
 260 int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
 261 {
 262         void __user *argp = (void __user *)arg;
 263         long r = -EINVAL;
 264
 265         if (!capable(CAP_SYS_ADMIN))
 266                 return -EPERM;
 267
 268         switch (ioctl) {
 269         case KVM_TRACE_ENABLE:
 270                 r = kvm_trace_enable(argp);
 271                 break;
 272         case KVM_TRACE_PAUSE:
 273                 r = kvm_trace_pause();
 274                 break;
 275         case KVM_TRACE_DISABLE:
 276                 r = 0;
 277                 kvm_trace_cleanup();
 278                 break;
 279         }
 280
 281         return r;
 282 }