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 #include <linux/ktime.h>
  21
  22 #include <linux/kvm_host.h>
  23
  24 #define KVM_TRACE_STATE_RUNNING         (1 << 0)
  25 #define KVM_TRACE_STATE_PAUSE           (1 << 1)
  26 #define KVM_TRACE_STATE_CLEARUP         (1 << 2)
  27
  28 struct kvm_trace {
  29         int trace_state;
  30         struct rchan *rchan;
  31         struct dentry *lost_file;
  32         atomic_t lost_records;
  33 };
  34 static struct kvm_trace *kvm_trace;
  35
  36 struct kvm_trace_probe {
  37         const char *name;
  38         const char *format;
  39         u32 timestamp_in;
  40         marker_probe_func *probe_func;
  41 };
  42
  43 static inline int calc_rec_size(int timestamp, int extra)
  44 {
  45         int rec_size = KVM_TRC_HEAD_SIZE;
  46
  47         rec_size += extra;
  48         return timestamp ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
  49 }
  50
  51 static void kvm_add_trace(void *probe_private, void *call_data,
  52                           const char *format, va_list *args)
  53 {
  54         struct kvm_trace_probe *p = probe_private;
  55         struct kvm_trace *kt = kvm_trace;
  56         struct kvm_trace_rec rec;
  57         struct kvm_vcpu *vcpu;
  58         int    i, size;
  59         u32    extra;
  60
  61         if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
  62                 return;
  63
  64         rec.rec_val     = TRACE_REC_EVENT_ID(va_arg(*args, u32));
  65         vcpu            = va_arg(*args, struct kvm_vcpu *);
  66         rec.pid         = current->tgid;
  67         rec.vcpu_id     = vcpu->vcpu_id;
  68
  69         extra           = va_arg(*args, u32);
  70         WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
  71         extra           = min_t(u32, extra, KVM_TRC_EXTRA_MAX);
  72
  73         rec.rec_val |= TRACE_REC_TCS(p->timestamp_in)
  74                         | TRACE_REC_NUM_DATA_ARGS(extra);
  75
  76         if (p->timestamp_in) {
  77                 rec.u.timestamp.timestamp = ktime_to_ns(ktime_get());
  78
  79                 for (i = 0; i < extra; i++)
  80                         rec.u.timestamp.extra_u32[i] = va_arg(*args, u32);
  81         } else {
  82                 for (i = 0; i < extra; i++)
  83                         rec.u.notimestamp.extra_u32[i] = va_arg(*args, u32);
  84         }
  85
  86         size = calc_rec_size(p->timestamp_in, extra * sizeof(u32));
  87         relay_write(kt->rchan, &rec, size);
  88 }
  89
  90 static struct kvm_trace_probe kvm_trace_probes[] = {
  91         { "kvm_trace_entryexit", "%u %p %u %u %u %u %u %u", 1, kvm_add_trace },
  92         { "kvm_trace_handler", "%u %p %u %u %u %u %u %u", 0, kvm_add_trace },
  93 };
  94
  95 static int lost_records_get(void *data, u64 *val)
  96 {
  97         struct kvm_trace *kt = data;
  98
  99         *val = atomic_read(&kt->lost_records);
 100         return 0;
 101 }
 102
 103 DEFINE_SIMPLE_ATTRIBUTE(kvm_trace_lost_ops, lost_records_get, NULL, "%llu\n");
 104
 105 /*
 106  *  The relay channel is used in "no-overwrite" mode, it keeps trace of how
 107  *  many times we encountered a full subbuffer, to tell user space app the
 108  *  lost records there were.
 109  */
 110 static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 111                                      void *prev_subbuf, size_t prev_padding)
 112 {
 113         struct kvm_trace *kt;
 114
 115         if (!relay_buf_full(buf)) {
 116                 if (!prev_subbuf) {
 117                         /*
 118                          * executed only once when the channel is opened
 119                          * save metadata as first record
 120                          */
 121                         subbuf_start_reserve(buf, sizeof(u32));
 122                         *(u32 *)subbuf = 0x12345678;
 123                 }
 124
 125                 return 1;
 126         }
 127
 128         kt = buf->chan->private_data;
 129         atomic_inc(&kt->lost_records);
 130
 131         return 0;
 132 }
 133
 134 static struct dentry *kvm_create_buf_file_callack(const char *filename,
 135                                                  struct dentry *parent,
 136                                                  int mode,
 137                                                  struct rchan_buf *buf,
 138                                                  int *is_global)
 139 {
 140         return debugfs_create_file(filename, mode, parent, buf,
 141                                    &relay_file_operations);
 142 }
 143
 144 static int kvm_remove_buf_file_callback(struct dentry *dentry)
 145 {
 146         debugfs_remove(dentry);
 147         return 0;
 148 }
 149
 150 static struct rchan_callbacks kvm_relay_callbacks = {
 151         .subbuf_start           = kvm_subbuf_start_callback,
 152         .create_buf_file        = kvm_create_buf_file_callack,
 153         .remove_buf_file        = kvm_remove_buf_file_callback,
 154 };
 155
 156 static int do_kvm_trace_enable(struct kvm_user_trace_setup *kuts)
 157 {
 158         struct kvm_trace *kt;
 159         int i, r = -ENOMEM;
 160
 161         if (!kuts->buf_size || !kuts->buf_nr)
 162                 return -EINVAL;
 163
 164         kt = kzalloc(sizeof(*kt), GFP_KERNEL);
 165         if (!kt)
 166                 goto err;
 167
 168         r = -EIO;
 169         atomic_set(&kt->lost_records, 0);
 170         kt->lost_file = debugfs_create_file("lost_records", 0444, kvm_debugfs_dir,
 171                                             kt, &kvm_trace_lost_ops);
 172         if (!kt->lost_file)
 173                 goto err;
 174
 175         kt->rchan = relay_open("trace", kvm_debugfs_dir, kuts->buf_size,
 176                                 kuts->buf_nr, &kvm_relay_callbacks, kt);
 177         if (!kt->rchan)
 178                 goto err;
 179
 180         kvm_trace = kt;
 181
 182         for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 183                 struct kvm_trace_probe *p = &kvm_trace_probes[i];
 184
 185                 r = marker_probe_register(p->name, p->format, p->probe_func, p);
 186                 if (r)
 187                         printk(KERN_INFO "Unable to register probe %s\n",
 188                                p->name);
 189         }
 190
 191         kvm_trace->trace_state = KVM_TRACE_STATE_RUNNING;
 192
 193         return 0;
 194 err:
 195         if (kt) {
 196                 if (kt->lost_file)
 197                         debugfs_remove(kt->lost_file);
 198                 if (kt->rchan)
 199                         relay_close(kt->rchan);
 200                 kfree(kt);
 201         }
 202         return r;
 203 }
 204
 205 static int kvm_trace_enable(char __user *arg)
 206 {
 207         struct kvm_user_trace_setup kuts;
 208         int ret;
 209
 210         ret = copy_from_user(&kuts, arg, sizeof(kuts));
 211         if (ret)
 212                 return -EFAULT;
 213
 214         ret = do_kvm_trace_enable(&kuts);
 215         if (ret)
 216                 return ret;
 217
 218         return 0;
 219 }
 220
 221 static int kvm_trace_pause(void)
 222 {
 223         struct kvm_trace *kt = kvm_trace;
 224         int r = -EINVAL;
 225
 226         if (kt == NULL)
 227                 return r;
 228
 229         if (kt->trace_state == KVM_TRACE_STATE_RUNNING) {
 230                 kt->trace_state = KVM_TRACE_STATE_PAUSE;
 231                 relay_flush(kt->rchan);
 232                 r = 0;
 233         }
 234
 235         return r;
 236 }
 237
 238 void kvm_trace_cleanup(void)
 239 {
 240         struct kvm_trace *kt = kvm_trace;
 241         int i;
 242
 243         if (kt == NULL)
 244                 return;
 245
 246         if (kt->trace_state == KVM_TRACE_STATE_RUNNING ||
 247             kt->trace_state == KVM_TRACE_STATE_PAUSE) {
 248
 249                 kt->trace_state = KVM_TRACE_STATE_CLEARUP;
 250
 251                 for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
 252                         struct kvm_trace_probe *p = &kvm_trace_probes[i];
 253                         marker_probe_unregister(p->name, p->probe_func, p);
 254                 }
 255
 256                 relay_close(kt->rchan);
 257                 debugfs_remove(kt->lost_file);
 258                 kfree(kt);
 259         }
 260 }
 261
 262 int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
 263 {
 264         void __user *argp = (void __user *)arg;
 265         long r = -EINVAL;
 266
 267         if (!capable(CAP_SYS_ADMIN))
 268                 return -EPERM;
 269
 270         switch (ioctl) {
 271         case KVM_TRACE_ENABLE:
 272                 r = kvm_trace_enable(argp);
 273                 break;
 274         case KVM_TRACE_PAUSE:
 275                 r = kvm_trace_pause();
 276                 break;
 277         case KVM_TRACE_DISABLE:
 278                 r = 0;
 279                 kvm_trace_cleanup();
 280                 break;
 281         }
 282
 283         return r;
 284 }