1 /*
2  * Virtual Processor Dispatch Trace Log
3  *
4  * (C) Copyright IBM Corporation 2009
5  *
6  * Author: Jeremy Kerr <jk@ozlabs.org>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2, or (at your option)
11  * any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21  */
22 
23 #include <linux/init.h>
24 #include <linux/slab.h>
25 #include <linux/debugfs.h>
26 #include <linux/spinlock.h>
27 #include <asm/smp.h>
28 #include <asm/uaccess.h>
29 #include <asm/firmware.h>
30 #include <asm/lppaca.h>
31 #include <asm/debug.h>
32 
33 #include "plpar_wrappers.h"
34 
35 struct dtl {
36 	struct dtl_entry	*buf;
37 	struct dentry		*file;
38 	int			cpu;
39 	int			buf_entries;
40 	u64			last_idx;
41 	spinlock_t		lock;
42 };
43 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
44 
45 /*
46  * Dispatch trace log event mask:
47  * 0x7: 0x1: voluntary virtual processor waits
48  *      0x2: time-slice preempts
49  *      0x4: virtual partition memory page faults
50  */
51 static u8 dtl_event_mask = 0x7;
52 
53 
54 /*
55  * Size of per-cpu log buffers. Firmware requires that the buffer does
56  * not cross a 4k boundary.
57  */
58 static int dtl_buf_entries = N_DISPATCH_LOG;
59 
60 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
61 struct dtl_ring {
62 	u64	write_index;
63 	struct dtl_entry *write_ptr;
64 	struct dtl_entry *buf;
65 	struct dtl_entry *buf_end;
66 	u8	saved_dtl_mask;
67 };
68 
69 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
70 
71 static atomic_t dtl_count;
72 
73 /*
74  * The cpu accounting code controls the DTL ring buffer, and we get
75  * given entries as they are processed.
76  */
77 static void consume_dtle(struct dtl_entry *dtle, u64 index)
78 {
79 	struct dtl_ring *dtlr = &__get_cpu_var(dtl_rings);
80 	struct dtl_entry *wp = dtlr->write_ptr;
81 	struct lppaca *vpa = local_paca->lppaca_ptr;
82 
83 	if (!wp)
84 		return;
85 
86 	*wp = *dtle;
87 	barrier();
88 
89 	/* check for hypervisor ring buffer overflow, ignore this entry if so */
90 	if (index + N_DISPATCH_LOG < vpa->dtl_idx)
91 		return;
92 
93 	++wp;
94 	if (wp == dtlr->buf_end)
95 		wp = dtlr->buf;
96 	dtlr->write_ptr = wp;
97 
98 	/* incrementing write_index makes the new entry visible */
99 	smp_wmb();
100 	++dtlr->write_index;
101 }
102 
103 static int dtl_start(struct dtl *dtl)
104 {
105 	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
106 
107 	dtlr->buf = dtl->buf;
108 	dtlr->buf_end = dtl->buf + dtl->buf_entries;
109 	dtlr->write_index = 0;
110 
111 	/* setting write_ptr enables logging into our buffer */
112 	smp_wmb();
113 	dtlr->write_ptr = dtl->buf;
114 
115 	/* enable event logging */
116 	dtlr->saved_dtl_mask = lppaca_of(dtl->cpu).dtl_enable_mask;
117 	lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
118 
119 	dtl_consumer = consume_dtle;
120 	atomic_inc(&dtl_count);
121 	return 0;
122 }
123 
124 static void dtl_stop(struct dtl *dtl)
125 {
126 	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
127 
128 	dtlr->write_ptr = NULL;
129 	smp_wmb();
130 
131 	dtlr->buf = NULL;
132 
133 	/* restore dtl_enable_mask */
134 	lppaca_of(dtl->cpu).dtl_enable_mask = dtlr->saved_dtl_mask;
135 
136 	if (atomic_dec_and_test(&dtl_count))
137 		dtl_consumer = NULL;
138 }
139 
140 static u64 dtl_current_index(struct dtl *dtl)
141 {
142 	return per_cpu(dtl_rings, dtl->cpu).write_index;
143 }
144 
145 #else /* CONFIG_VIRT_CPU_ACCOUNTING */
146 
147 static int dtl_start(struct dtl *dtl)
148 {
149 	unsigned long addr;
150 	int ret, hwcpu;
151 
152 	/* Register our dtl buffer with the hypervisor. The HV expects the
153 	 * buffer size to be passed in the second word of the buffer */
154 	((u32 *)dtl->buf)[1] = DISPATCH_LOG_BYTES;
155 
156 	hwcpu = get_hard_smp_processor_id(dtl->cpu);
157 	addr = __pa(dtl->buf);
158 	ret = register_dtl(hwcpu, addr);
159 	if (ret) {
160 		printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
161 		       "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
162 		return -EIO;
163 	}
164 
165 	/* set our initial buffer indices */
166 	lppaca_of(dtl->cpu).dtl_idx = 0;
167 
168 	/* ensure that our updates to the lppaca fields have occurred before
169 	 * we actually enable the logging */
170 	smp_wmb();
171 
172 	/* enable event logging */
173 	lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
174 
175 	return 0;
176 }
177 
178 static void dtl_stop(struct dtl *dtl)
179 {
180 	int hwcpu = get_hard_smp_processor_id(dtl->cpu);
181 
182 	lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
183 
184 	unregister_dtl(hwcpu);
185 }
186 
187 static u64 dtl_current_index(struct dtl *dtl)
188 {
189 	return lppaca_of(dtl->cpu).dtl_idx;
190 }
191 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
192 
193 static int dtl_enable(struct dtl *dtl)
194 {
195 	long int n_entries;
196 	long int rc;
197 	struct dtl_entry *buf = NULL;
198 
199 	if (!dtl_cache)
200 		return -ENOMEM;
201 
202 	/* only allow one reader */
203 	if (dtl->buf)
204 		return -EBUSY;
205 
206 	n_entries = dtl_buf_entries;
207 	buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
208 	if (!buf) {
209 		printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
210 				__func__, dtl->cpu);
211 		return -ENOMEM;
212 	}
213 
214 	spin_lock(&dtl->lock);
215 	rc = -EBUSY;
216 	if (!dtl->buf) {
217 		/* store the original allocation size for use during read */
218 		dtl->buf_entries = n_entries;
219 		dtl->buf = buf;
220 		dtl->last_idx = 0;
221 		rc = dtl_start(dtl);
222 		if (rc)
223 			dtl->buf = NULL;
224 	}
225 	spin_unlock(&dtl->lock);
226 
227 	if (rc)
228 		kmem_cache_free(dtl_cache, buf);
229 	return rc;
230 }
231 
232 static void dtl_disable(struct dtl *dtl)
233 {
234 	spin_lock(&dtl->lock);
235 	dtl_stop(dtl);
236 	kmem_cache_free(dtl_cache, dtl->buf);
237 	dtl->buf = NULL;
238 	dtl->buf_entries = 0;
239 	spin_unlock(&dtl->lock);
240 }
241 
242 /* file interface */
243 
244 static int dtl_file_open(struct inode *inode, struct file *filp)
245 {
246 	struct dtl *dtl = inode->i_private;
247 	int rc;
248 
249 	rc = dtl_enable(dtl);
250 	if (rc)
251 		return rc;
252 
253 	filp->private_data = dtl;
254 	return 0;
255 }
256 
257 static int dtl_file_release(struct inode *inode, struct file *filp)
258 {
259 	struct dtl *dtl = inode->i_private;
260 	dtl_disable(dtl);
261 	return 0;
262 }
263 
264 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
265 		loff_t *pos)
266 {
267 	long int rc, n_read, n_req, read_size;
268 	struct dtl *dtl;
269 	u64 cur_idx, last_idx, i;
270 
271 	if ((len % sizeof(struct dtl_entry)) != 0)
272 		return -EINVAL;
273 
274 	dtl = filp->private_data;
275 
276 	/* requested number of entries to read */
277 	n_req = len / sizeof(struct dtl_entry);
278 
279 	/* actual number of entries read */
280 	n_read = 0;
281 
282 	spin_lock(&dtl->lock);
283 
284 	cur_idx = dtl_current_index(dtl);
285 	last_idx = dtl->last_idx;
286 
287 	if (last_idx + dtl->buf_entries <= cur_idx)
288 		last_idx = cur_idx - dtl->buf_entries + 1;
289 
290 	if (last_idx + n_req > cur_idx)
291 		n_req = cur_idx - last_idx;
292 
293 	if (n_req > 0)
294 		dtl->last_idx = last_idx + n_req;
295 
296 	spin_unlock(&dtl->lock);
297 
298 	if (n_req <= 0)
299 		return 0;
300 
301 	i = last_idx % dtl->buf_entries;
302 
303 	/* read the tail of the buffer if we've wrapped */
304 	if (i + n_req > dtl->buf_entries) {
305 		read_size = dtl->buf_entries - i;
306 
307 		rc = copy_to_user(buf, &dtl->buf[i],
308 				read_size * sizeof(struct dtl_entry));
309 		if (rc)
310 			return -EFAULT;
311 
312 		i = 0;
313 		n_req -= read_size;
314 		n_read += read_size;
315 		buf += read_size * sizeof(struct dtl_entry);
316 	}
317 
318 	/* .. and now the head */
319 	rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
320 	if (rc)
321 		return -EFAULT;
322 
323 	n_read += n_req;
324 
325 	return n_read * sizeof(struct dtl_entry);
326 }
327 
328 static const struct file_operations dtl_fops = {
329 	.open		= dtl_file_open,
330 	.release	= dtl_file_release,
331 	.read		= dtl_file_read,
332 	.llseek		= no_llseek,
333 };
334 
335 static struct dentry *dtl_dir;
336 
337 static int dtl_setup_file(struct dtl *dtl)
338 {
339 	char name[10];
340 
341 	sprintf(name, "cpu-%d", dtl->cpu);
342 
343 	dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
344 	if (!dtl->file)
345 		return -ENOMEM;
346 
347 	return 0;
348 }
349 
350 static int dtl_init(void)
351 {
352 	struct dentry *event_mask_file, *buf_entries_file;
353 	int rc, i;
354 
355 	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
356 		return -ENODEV;
357 
358 	/* set up common debugfs structure */
359 
360 	rc = -ENOMEM;
361 	dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
362 	if (!dtl_dir) {
363 		printk(KERN_WARNING "%s: can't create dtl root dir\n",
364 				__func__);
365 		goto err;
366 	}
367 
368 	event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
369 				dtl_dir, &dtl_event_mask);
370 	buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0400,
371 				dtl_dir, &dtl_buf_entries);
372 
373 	if (!event_mask_file || !buf_entries_file) {
374 		printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
375 		goto err_remove_dir;
376 	}
377 
378 	/* set up the per-cpu log structures */
379 	for_each_possible_cpu(i) {
380 		struct dtl *dtl = &per_cpu(cpu_dtl, i);
381 		spin_lock_init(&dtl->lock);
382 		dtl->cpu = i;
383 
384 		rc = dtl_setup_file(dtl);
385 		if (rc)
386 			goto err_remove_dir;
387 	}
388 
389 	return 0;
390 
391 err_remove_dir:
392 	debugfs_remove_recursive(dtl_dir);
393 err:
394 	return rc;
395 }
396 arch_initcall(dtl_init);
397