1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Virtual Processor Dispatch Trace Log
4 *
5 * (C) Copyright IBM Corporation 2009
6 *
7 * Author: Jeremy Kerr <jk@ozlabs.org>
8 */
9
10 #include <linux/slab.h>
11 #include <linux/spinlock.h>
12 #include <asm/smp.h>
13 #include <linux/uaccess.h>
14 #include <linux/debugfs.h>
15 #include <asm/firmware.h>
16 #include <asm/dtl.h>
17 #include <asm/lppaca.h>
18 #include <asm/plpar_wrappers.h>
19 #include <asm/machdep.h>
20
21 #ifdef CONFIG_DTL
22 struct dtl {
23 struct dtl_entry *buf;
24 int cpu;
25 int buf_entries;
26 u64 last_idx;
27 spinlock_t lock;
28 };
29 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
30
31 static u8 dtl_event_mask = DTL_LOG_ALL;
32
33
34 /*
35 * Size of per-cpu log buffers. Firmware requires that the buffer does
36 * not cross a 4k boundary.
37 */
38 static int dtl_buf_entries = N_DISPATCH_LOG;
39
40 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
41
42 /*
43 * When CONFIG_VIRT_CPU_ACCOUNTING_NATIVE = y, the cpu accounting code controls
44 * reading from the dispatch trace log. If other code wants to consume
45 * DTL entries, it can set this pointer to a function that will get
46 * called once for each DTL entry that gets processed.
47 */
48 static void (*dtl_consumer)(struct dtl_entry *entry, u64 index);
49
50 struct dtl_ring {
51 u64 write_index;
52 struct dtl_entry *write_ptr;
53 struct dtl_entry *buf;
54 struct dtl_entry *buf_end;
55 };
56
57 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
58
59 static atomic_t dtl_count;
60
61 /*
62 * The cpu accounting code controls the DTL ring buffer, and we get
63 * given entries as they are processed.
64 */
consume_dtle(struct dtl_entry * dtle,u64 index)65 static void consume_dtle(struct dtl_entry *dtle, u64 index)
66 {
67 struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
68 struct dtl_entry *wp = dtlr->write_ptr;
69 struct lppaca *vpa = local_paca->lppaca_ptr;
70
71 if (!wp)
72 return;
73
74 *wp = *dtle;
75 barrier();
76
77 /* check for hypervisor ring buffer overflow, ignore this entry if so */
78 if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
79 return;
80
81 ++wp;
82 if (wp == dtlr->buf_end)
83 wp = dtlr->buf;
84 dtlr->write_ptr = wp;
85
86 /* incrementing write_index makes the new entry visible */
87 smp_wmb();
88 ++dtlr->write_index;
89 }
90
dtl_start(struct dtl * dtl)91 static int dtl_start(struct dtl *dtl)
92 {
93 struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
94
95 dtlr->buf = dtl->buf;
96 dtlr->buf_end = dtl->buf + dtl->buf_entries;
97 dtlr->write_index = 0;
98
99 /* setting write_ptr enables logging into our buffer */
100 smp_wmb();
101 dtlr->write_ptr = dtl->buf;
102
103 /* enable event logging */
104 lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
105
106 dtl_consumer = consume_dtle;
107 atomic_inc(&dtl_count);
108 return 0;
109 }
110
dtl_stop(struct dtl * dtl)111 static void dtl_stop(struct dtl *dtl)
112 {
113 struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
114
115 dtlr->write_ptr = NULL;
116 smp_wmb();
117
118 dtlr->buf = NULL;
119
120 /* restore dtl_enable_mask */
121 lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
122
123 if (atomic_dec_and_test(&dtl_count))
124 dtl_consumer = NULL;
125 }
126
dtl_current_index(struct dtl * dtl)127 static u64 dtl_current_index(struct dtl *dtl)
128 {
129 return per_cpu(dtl_rings, dtl->cpu).write_index;
130 }
131
132 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
133
dtl_start(struct dtl * dtl)134 static int dtl_start(struct dtl *dtl)
135 {
136 unsigned long addr;
137 int ret, hwcpu;
138
139 /* Register our dtl buffer with the hypervisor. The HV expects the
140 * buffer size to be passed in the second word of the buffer */
141 ((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);
142
143 hwcpu = get_hard_smp_processor_id(dtl->cpu);
144 addr = __pa(dtl->buf);
145 ret = register_dtl(hwcpu, addr);
146 if (ret) {
147 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
148 "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
149 return -EIO;
150 }
151
152 /* set our initial buffer indices */
153 lppaca_of(dtl->cpu).dtl_idx = 0;
154
155 /* ensure that our updates to the lppaca fields have occurred before
156 * we actually enable the logging */
157 smp_wmb();
158
159 /* enable event logging */
160 lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
161
162 return 0;
163 }
164
dtl_stop(struct dtl * dtl)165 static void dtl_stop(struct dtl *dtl)
166 {
167 int hwcpu = get_hard_smp_processor_id(dtl->cpu);
168
169 lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
170
171 unregister_dtl(hwcpu);
172 }
173
dtl_current_index(struct dtl * dtl)174 static u64 dtl_current_index(struct dtl *dtl)
175 {
176 return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
177 }
178 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
179
dtl_enable(struct dtl * dtl)180 static int dtl_enable(struct dtl *dtl)
181 {
182 long int n_entries;
183 long int rc;
184 struct dtl_entry *buf = NULL;
185
186 if (!dtl_cache)
187 return -ENOMEM;
188
189 /* only allow one reader */
190 if (dtl->buf)
191 return -EBUSY;
192
193 /* ensure there are no other conflicting dtl users */
194 if (!read_trylock(&dtl_access_lock))
195 return -EBUSY;
196
197 n_entries = dtl_buf_entries;
198 buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
199 if (!buf) {
200 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
201 __func__, dtl->cpu);
202 read_unlock(&dtl_access_lock);
203 return -ENOMEM;
204 }
205
206 spin_lock(&dtl->lock);
207 rc = -EBUSY;
208 if (!dtl->buf) {
209 /* store the original allocation size for use during read */
210 dtl->buf_entries = n_entries;
211 dtl->buf = buf;
212 dtl->last_idx = 0;
213 rc = dtl_start(dtl);
214 if (rc)
215 dtl->buf = NULL;
216 }
217 spin_unlock(&dtl->lock);
218
219 if (rc) {
220 read_unlock(&dtl_access_lock);
221 kmem_cache_free(dtl_cache, buf);
222 }
223
224 return rc;
225 }
226
dtl_disable(struct dtl * dtl)227 static void dtl_disable(struct dtl *dtl)
228 {
229 spin_lock(&dtl->lock);
230 dtl_stop(dtl);
231 kmem_cache_free(dtl_cache, dtl->buf);
232 dtl->buf = NULL;
233 dtl->buf_entries = 0;
234 spin_unlock(&dtl->lock);
235 read_unlock(&dtl_access_lock);
236 }
237
238 /* file interface */
239
dtl_file_open(struct inode * inode,struct file * filp)240 static int dtl_file_open(struct inode *inode, struct file *filp)
241 {
242 struct dtl *dtl = inode->i_private;
243 int rc;
244
245 rc = dtl_enable(dtl);
246 if (rc)
247 return rc;
248
249 filp->private_data = dtl;
250 return 0;
251 }
252
dtl_file_release(struct inode * inode,struct file * filp)253 static int dtl_file_release(struct inode *inode, struct file *filp)
254 {
255 struct dtl *dtl = inode->i_private;
256 dtl_disable(dtl);
257 return 0;
258 }
259
dtl_file_read(struct file * filp,char __user * buf,size_t len,loff_t * pos)260 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
261 loff_t *pos)
262 {
263 long int rc, n_read, n_req, read_size;
264 struct dtl *dtl;
265 u64 cur_idx, last_idx, i;
266
267 if ((len % sizeof(struct dtl_entry)) != 0)
268 return -EINVAL;
269
270 dtl = filp->private_data;
271
272 /* requested number of entries to read */
273 n_req = len / sizeof(struct dtl_entry);
274
275 /* actual number of entries read */
276 n_read = 0;
277
278 spin_lock(&dtl->lock);
279
280 cur_idx = dtl_current_index(dtl);
281 last_idx = dtl->last_idx;
282
283 if (last_idx + dtl->buf_entries <= cur_idx)
284 last_idx = cur_idx - dtl->buf_entries + 1;
285
286 if (last_idx + n_req > cur_idx)
287 n_req = cur_idx - last_idx;
288
289 if (n_req > 0)
290 dtl->last_idx = last_idx + n_req;
291
292 spin_unlock(&dtl->lock);
293
294 if (n_req <= 0)
295 return 0;
296
297 i = last_idx % dtl->buf_entries;
298
299 /* read the tail of the buffer if we've wrapped */
300 if (i + n_req > dtl->buf_entries) {
301 read_size = dtl->buf_entries - i;
302
303 rc = copy_to_user(buf, &dtl->buf[i],
304 read_size * sizeof(struct dtl_entry));
305 if (rc)
306 return -EFAULT;
307
308 i = 0;
309 n_req -= read_size;
310 n_read += read_size;
311 buf += read_size * sizeof(struct dtl_entry);
312 }
313
314 /* .. and now the head */
315 rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
316 if (rc)
317 return -EFAULT;
318
319 n_read += n_req;
320
321 return n_read * sizeof(struct dtl_entry);
322 }
323
324 static const struct file_operations dtl_fops = {
325 .open = dtl_file_open,
326 .release = dtl_file_release,
327 .read = dtl_file_read,
328 .llseek = no_llseek,
329 };
330
331 static struct dentry *dtl_dir;
332
dtl_setup_file(struct dtl * dtl)333 static void dtl_setup_file(struct dtl *dtl)
334 {
335 char name[10];
336
337 sprintf(name, "cpu-%d", dtl->cpu);
338
339 debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
340 }
341
dtl_init(void)342 static int dtl_init(void)
343 {
344 int i;
345
346 if (!firmware_has_feature(FW_FEATURE_SPLPAR))
347 return -ENODEV;
348
349 /* set up common debugfs structure */
350
351 dtl_dir = debugfs_create_dir("dtl", arch_debugfs_dir);
352
353 debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
354 debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);
355
356 /* set up the per-cpu log structures */
357 for_each_possible_cpu(i) {
358 struct dtl *dtl = &per_cpu(cpu_dtl, i);
359 spin_lock_init(&dtl->lock);
360 dtl->cpu = i;
361
362 dtl_setup_file(dtl);
363 }
364
365 return 0;
366 }
367 machine_arch_initcall(pseries, dtl_init);
368 #endif /* CONFIG_DTL */
369
370 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
371 /*
372 * Scan the dispatch trace log and count up the stolen time.
373 * Should be called with interrupts disabled.
374 */
scan_dispatch_log(u64 stop_tb)375 static notrace u64 scan_dispatch_log(u64 stop_tb)
376 {
377 u64 i = local_paca->dtl_ridx;
378 struct dtl_entry *dtl = local_paca->dtl_curr;
379 struct dtl_entry *dtl_end = local_paca->dispatch_log_end;
380 struct lppaca *vpa = local_paca->lppaca_ptr;
381 u64 tb_delta;
382 u64 stolen = 0;
383 u64 dtb;
384
385 if (!dtl)
386 return 0;
387
388 if (i == be64_to_cpu(vpa->dtl_idx))
389 return 0;
390 while (i < be64_to_cpu(vpa->dtl_idx)) {
391 dtb = be64_to_cpu(dtl->timebase);
392 tb_delta = be32_to_cpu(dtl->enqueue_to_dispatch_time) +
393 be32_to_cpu(dtl->ready_to_enqueue_time);
394 barrier();
395 if (i + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx)) {
396 /* buffer has overflowed */
397 i = be64_to_cpu(vpa->dtl_idx) - N_DISPATCH_LOG;
398 dtl = local_paca->dispatch_log + (i % N_DISPATCH_LOG);
399 continue;
400 }
401 if (dtb > stop_tb)
402 break;
403 #ifdef CONFIG_DTL
404 if (dtl_consumer)
405 dtl_consumer(dtl, i);
406 #endif
407 stolen += tb_delta;
408 ++i;
409 ++dtl;
410 if (dtl == dtl_end)
411 dtl = local_paca->dispatch_log;
412 }
413 local_paca->dtl_ridx = i;
414 local_paca->dtl_curr = dtl;
415 return stolen;
416 }
417
418 /*
419 * Accumulate stolen time by scanning the dispatch trace log.
420 * Called on entry from user mode.
421 */
pseries_accumulate_stolen_time(void)422 void notrace pseries_accumulate_stolen_time(void)
423 {
424 u64 sst, ust;
425 struct cpu_accounting_data *acct = &local_paca->accounting;
426
427 sst = scan_dispatch_log(acct->starttime_user);
428 ust = scan_dispatch_log(acct->starttime);
429 acct->stime -= sst;
430 acct->utime -= ust;
431 acct->steal_time += ust + sst;
432 }
433
pseries_calculate_stolen_time(u64 stop_tb)434 u64 pseries_calculate_stolen_time(u64 stop_tb)
435 {
436 if (!firmware_has_feature(FW_FEATURE_SPLPAR))
437 return 0;
438
439 if (get_paca()->dtl_ridx != be64_to_cpu(get_lppaca()->dtl_idx))
440 return scan_dispatch_log(stop_tb);
441
442 return 0;
443 }
444
445 #endif
446