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/slab.h>
24 #include <linux/debugfs.h>
25 #include <linux/spinlock.h>
26 #include <asm/smp.h>
27 #include <asm/uaccess.h>
28 #include <asm/firmware.h>
29 #include <asm/lppaca.h>
30 #include <asm/debug.h>
31 #include <asm/plpar_wrappers.h>
32 #include <asm/machdep.h>
33 
34 struct dtl {
35 	struct dtl_entry	*buf;
36 	struct dentry		*file;
37 	int			cpu;
38 	int			buf_entries;
39 	u64			last_idx;
40 	spinlock_t		lock;
41 };
42 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
43 
44 /*
45  * Dispatch trace log event mask:
46  * 0x7: 0x1: voluntary virtual processor waits
47  *      0x2: time-slice preempts
48  *      0x4: virtual partition memory page faults
49  */
50 static u8 dtl_event_mask = 0x7;
51 
52 
53 /*
54  * Size of per-cpu log buffers. Firmware requires that the buffer does
55  * not cross a 4k boundary.
56  */
57 static int dtl_buf_entries = N_DISPATCH_LOG;
58 
59 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
60 struct dtl_ring {
61 	u64	write_index;
62 	struct dtl_entry *write_ptr;
63 	struct dtl_entry *buf;
64 	struct dtl_entry *buf_end;
65 	u8	saved_dtl_mask;
66 };
67 
68 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
69 
70 static atomic_t dtl_count;
71 
72 /*
73  * The cpu accounting code controls the DTL ring buffer, and we get
74  * given entries as they are processed.
75  */
76 static void consume_dtle(struct dtl_entry *dtle, u64 index)
77 {
78 	struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
79 	struct dtl_entry *wp = dtlr->write_ptr;
80 	struct lppaca *vpa = local_paca->lppaca_ptr;
81 
82 	if (!wp)
83 		return;
84 
85 	*wp = *dtle;
86 	barrier();
87 
88 	/* check for hypervisor ring buffer overflow, ignore this entry if so */
89 	if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
90 		return;
91 
92 	++wp;
93 	if (wp == dtlr->buf_end)
94 		wp = dtlr->buf;
95 	dtlr->write_ptr = wp;
96 
97 	/* incrementing write_index makes the new entry visible */
98 	smp_wmb();
99 	++dtlr->write_index;
100 }
101 
102 static int dtl_start(struct dtl *dtl)
103 {
104 	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
105 
106 	dtlr->buf = dtl->buf;
107 	dtlr->buf_end = dtl->buf + dtl->buf_entries;
108 	dtlr->write_index = 0;
109 
110 	/* setting write_ptr enables logging into our buffer */
111 	smp_wmb();
112 	dtlr->write_ptr = dtl->buf;
113 
114 	/* enable event logging */
115 	dtlr->saved_dtl_mask = lppaca_of(dtl->cpu).dtl_enable_mask;
116 	lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
117 
118 	dtl_consumer = consume_dtle;
119 	atomic_inc(&dtl_count);
120 	return 0;
121 }
122 
123 static void dtl_stop(struct dtl *dtl)
124 {
125 	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
126 
127 	dtlr->write_ptr = NULL;
128 	smp_wmb();
129 
130 	dtlr->buf = NULL;
131 
132 	/* restore dtl_enable_mask */
133 	lppaca_of(dtl->cpu).dtl_enable_mask = dtlr->saved_dtl_mask;
134 
135 	if (atomic_dec_and_test(&dtl_count))
136 		dtl_consumer = NULL;
137 }
138 
139 static u64 dtl_current_index(struct dtl *dtl)
140 {
141 	return per_cpu(dtl_rings, dtl->cpu).write_index;
142 }
143 
144 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
145 
146 static int dtl_start(struct dtl *dtl)
147 {
148 	unsigned long addr;
149 	int ret, hwcpu;
150 
151 	/* Register our dtl buffer with the hypervisor. The HV expects the
152 	 * buffer size to be passed in the second word of the buffer */
153 	((u32 *)dtl->buf)[1] = DISPATCH_LOG_BYTES;
154 
155 	hwcpu = get_hard_smp_processor_id(dtl->cpu);
156 	addr = __pa(dtl->buf);
157 	ret = register_dtl(hwcpu, addr);
158 	if (ret) {
159 		printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
160 		       "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
161 		return -EIO;
162 	}
163 
164 	/* set our initial buffer indices */
165 	lppaca_of(dtl->cpu).dtl_idx = 0;
166 
167 	/* ensure that our updates to the lppaca fields have occurred before
168 	 * we actually enable the logging */
169 	smp_wmb();
170 
171 	/* enable event logging */
172 	lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
173 
174 	return 0;
175 }
176 
177 static void dtl_stop(struct dtl *dtl)
178 {
179 	int hwcpu = get_hard_smp_processor_id(dtl->cpu);
180 
181 	lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
182 
183 	unregister_dtl(hwcpu);
184 }
185 
186 static u64 dtl_current_index(struct dtl *dtl)
187 {
188 	return lppaca_of(dtl->cpu).dtl_idx;
189 }
190 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
191 
192 static int dtl_enable(struct dtl *dtl)
193 {
194 	long int n_entries;
195 	long int rc;
196 	struct dtl_entry *buf = NULL;
197 
198 	if (!dtl_cache)
199 		return -ENOMEM;
200 
201 	/* only allow one reader */
202 	if (dtl->buf)
203 		return -EBUSY;
204 
205 	n_entries = dtl_buf_entries;
206 	buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
207 	if (!buf) {
208 		printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
209 				__func__, dtl->cpu);
210 		return -ENOMEM;
211 	}
212 
213 	spin_lock(&dtl->lock);
214 	rc = -EBUSY;
215 	if (!dtl->buf) {
216 		/* store the original allocation size for use during read */
217 		dtl->buf_entries = n_entries;
218 		dtl->buf = buf;
219 		dtl->last_idx = 0;
220 		rc = dtl_start(dtl);
221 		if (rc)
222 			dtl->buf = NULL;
223 	}
224 	spin_unlock(&dtl->lock);
225 
226 	if (rc)
227 		kmem_cache_free(dtl_cache, buf);
228 	return rc;
229 }
230 
231 static void dtl_disable(struct dtl *dtl)
232 {
233 	spin_lock(&dtl->lock);
234 	dtl_stop(dtl);
235 	kmem_cache_free(dtl_cache, dtl->buf);
236 	dtl->buf = NULL;
237 	dtl->buf_entries = 0;
238 	spin_unlock(&dtl->lock);
239 }
240 
241 /* file interface */
242 
243 static int dtl_file_open(struct inode *inode, struct file *filp)
244 {
245 	struct dtl *dtl = inode->i_private;
246 	int rc;
247 
248 	rc = dtl_enable(dtl);
249 	if (rc)
250 		return rc;
251 
252 	filp->private_data = dtl;
253 	return 0;
254 }
255 
256 static int dtl_file_release(struct inode *inode, struct file *filp)
257 {
258 	struct dtl *dtl = inode->i_private;
259 	dtl_disable(dtl);
260 	return 0;
261 }
262 
263 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
264 		loff_t *pos)
265 {
266 	long int rc, n_read, n_req, read_size;
267 	struct dtl *dtl;
268 	u64 cur_idx, last_idx, i;
269 
270 	if ((len % sizeof(struct dtl_entry)) != 0)
271 		return -EINVAL;
272 
273 	dtl = filp->private_data;
274 
275 	/* requested number of entries to read */
276 	n_req = len / sizeof(struct dtl_entry);
277 
278 	/* actual number of entries read */
279 	n_read = 0;
280 
281 	spin_lock(&dtl->lock);
282 
283 	cur_idx = dtl_current_index(dtl);
284 	last_idx = dtl->last_idx;
285 
286 	if (last_idx + dtl->buf_entries <= cur_idx)
287 		last_idx = cur_idx - dtl->buf_entries + 1;
288 
289 	if (last_idx + n_req > cur_idx)
290 		n_req = cur_idx - last_idx;
291 
292 	if (n_req > 0)
293 		dtl->last_idx = last_idx + n_req;
294 
295 	spin_unlock(&dtl->lock);
296 
297 	if (n_req <= 0)
298 		return 0;
299 
300 	i = last_idx % dtl->buf_entries;
301 
302 	/* read the tail of the buffer if we've wrapped */
303 	if (i + n_req > dtl->buf_entries) {
304 		read_size = dtl->buf_entries - i;
305 
306 		rc = copy_to_user(buf, &dtl->buf[i],
307 				read_size * sizeof(struct dtl_entry));
308 		if (rc)
309 			return -EFAULT;
310 
311 		i = 0;
312 		n_req -= read_size;
313 		n_read += read_size;
314 		buf += read_size * sizeof(struct dtl_entry);
315 	}
316 
317 	/* .. and now the head */
318 	rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
319 	if (rc)
320 		return -EFAULT;
321 
322 	n_read += n_req;
323 
324 	return n_read * sizeof(struct dtl_entry);
325 }
326 
327 static const struct file_operations dtl_fops = {
328 	.open		= dtl_file_open,
329 	.release	= dtl_file_release,
330 	.read		= dtl_file_read,
331 	.llseek		= no_llseek,
332 };
333 
334 static struct dentry *dtl_dir;
335 
336 static int dtl_setup_file(struct dtl *dtl)
337 {
338 	char name[10];
339 
340 	sprintf(name, "cpu-%d", dtl->cpu);
341 
342 	dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
343 	if (!dtl->file)
344 		return -ENOMEM;
345 
346 	return 0;
347 }
348 
349 static int dtl_init(void)
350 {
351 	struct dentry *event_mask_file, *buf_entries_file;
352 	int rc, i;
353 
354 	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
355 		return -ENODEV;
356 
357 	/* set up common debugfs structure */
358 
359 	rc = -ENOMEM;
360 	dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
361 	if (!dtl_dir) {
362 		printk(KERN_WARNING "%s: can't create dtl root dir\n",
363 				__func__);
364 		goto err;
365 	}
366 
367 	event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
368 				dtl_dir, &dtl_event_mask);
369 	buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0400,
370 				dtl_dir, &dtl_buf_entries);
371 
372 	if (!event_mask_file || !buf_entries_file) {
373 		printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
374 		goto err_remove_dir;
375 	}
376 
377 	/* set up the per-cpu log structures */
378 	for_each_possible_cpu(i) {
379 		struct dtl *dtl = &per_cpu(cpu_dtl, i);
380 		spin_lock_init(&dtl->lock);
381 		dtl->cpu = i;
382 
383 		rc = dtl_setup_file(dtl);
384 		if (rc)
385 			goto err_remove_dir;
386 	}
387 
388 	return 0;
389 
390 err_remove_dir:
391 	debugfs_remove_recursive(dtl_dir);
392 err:
393 	return rc;
394 }
395 machine_arch_initcall(pseries, dtl_init);
396