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 marker_synchronize_unregister();
256
257 relay_close(kt->rchan);
258 debugfs_remove(kt->lost_file);
259 kfree(kt);
260 }
261 }
262
263 int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
264 {
265 void __user *argp = (void __user *)arg;
266 long r = -EINVAL;
267
268 if (!capable(CAP_SYS_ADMIN))
269 return -EPERM;
270
271 switch (ioctl) {
272 case KVM_TRACE_ENABLE:
273 r = kvm_trace_enable(argp);
274 break;
275 case KVM_TRACE_PAUSE:
276 r = kvm_trace_pause();
277 break;
278 case KVM_TRACE_DISABLE:
279 r = 0;
280 kvm_trace_cleanup();
281 break;
282 }
283
284 return r;
285 }
286
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