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 struct dtl {
22 struct dtl_entry *buf;
23 int cpu;
24 int buf_entries;
25 u64 last_idx;
26 spinlock_t lock;
27 };
28 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
29
30 static u8 dtl_event_mask = DTL_LOG_ALL;
31
32
33 /*
34 * Size of per-cpu log buffers. Firmware requires that the buffer does
35 * not cross a 4k boundary.
36 */
37 static int dtl_buf_entries = N_DISPATCH_LOG;
38
39 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
40 struct dtl_ring {
41 u64 write_index;
42 struct dtl_entry *write_ptr;
43 struct dtl_entry *buf;
44 struct dtl_entry *buf_end;
45 };
46
47 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
48
49 static atomic_t dtl_count;
50
51 /*
52 * The cpu accounting code controls the DTL ring buffer, and we get
53 * given entries as they are processed.
54 */
consume_dtle(struct dtl_entry * dtle,u64 index)55 static void consume_dtle(struct dtl_entry *dtle, u64 index)
56 {
57 struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
58 struct dtl_entry *wp = dtlr->write_ptr;
59 struct lppaca *vpa = local_paca->lppaca_ptr;
60
61 if (!wp)
62 return;
63
64 *wp = *dtle;
65 barrier();
66
67 /* check for hypervisor ring buffer overflow, ignore this entry if so */
68 if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
69 return;
70
71 ++wp;
72 if (wp == dtlr->buf_end)
73 wp = dtlr->buf;
74 dtlr->write_ptr = wp;
75
76 /* incrementing write_index makes the new entry visible */
77 smp_wmb();
78 ++dtlr->write_index;
79 }
80
dtl_start(struct dtl * dtl)81 static int dtl_start(struct dtl *dtl)
82 {
83 struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
84
85 dtlr->buf = dtl->buf;
86 dtlr->buf_end = dtl->buf + dtl->buf_entries;
87 dtlr->write_index = 0;
88
89 /* setting write_ptr enables logging into our buffer */
90 smp_wmb();
91 dtlr->write_ptr = dtl->buf;
92
93 /* enable event logging */
94 lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
95
96 dtl_consumer = consume_dtle;
97 atomic_inc(&dtl_count);
98 return 0;
99 }
100
dtl_stop(struct dtl * dtl)101 static void dtl_stop(struct dtl *dtl)
102 {
103 struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
104
105 dtlr->write_ptr = NULL;
106 smp_wmb();
107
108 dtlr->buf = NULL;
109
110 /* restore dtl_enable_mask */
111 lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
112
113 if (atomic_dec_and_test(&dtl_count))
114 dtl_consumer = NULL;
115 }
116
dtl_current_index(struct dtl * dtl)117 static u64 dtl_current_index(struct dtl *dtl)
118 {
119 return per_cpu(dtl_rings, dtl->cpu).write_index;
120 }
121
122 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
123
dtl_start(struct dtl * dtl)124 static int dtl_start(struct dtl *dtl)
125 {
126 unsigned long addr;
127 int ret, hwcpu;
128
129 /* Register our dtl buffer with the hypervisor. The HV expects the
130 * buffer size to be passed in the second word of the buffer */
131 ((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);
132
133 hwcpu = get_hard_smp_processor_id(dtl->cpu);
134 addr = __pa(dtl->buf);
135 ret = register_dtl(hwcpu, addr);
136 if (ret) {
137 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
138 "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
139 return -EIO;
140 }
141
142 /* set our initial buffer indices */
143 lppaca_of(dtl->cpu).dtl_idx = 0;
144
145 /* ensure that our updates to the lppaca fields have occurred before
146 * we actually enable the logging */
147 smp_wmb();
148
149 /* enable event logging */
150 lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
151
152 return 0;
153 }
154
dtl_stop(struct dtl * dtl)155 static void dtl_stop(struct dtl *dtl)
156 {
157 int hwcpu = get_hard_smp_processor_id(dtl->cpu);
158
159 lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
160
161 unregister_dtl(hwcpu);
162 }
163
dtl_current_index(struct dtl * dtl)164 static u64 dtl_current_index(struct dtl *dtl)
165 {
166 return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
167 }
168 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
169
dtl_enable(struct dtl * dtl)170 static int dtl_enable(struct dtl *dtl)
171 {
172 long int n_entries;
173 long int rc;
174 struct dtl_entry *buf = NULL;
175
176 if (!dtl_cache)
177 return -ENOMEM;
178
179 /* only allow one reader */
180 if (dtl->buf)
181 return -EBUSY;
182
183 /* ensure there are no other conflicting dtl users */
184 if (!read_trylock(&dtl_access_lock))
185 return -EBUSY;
186
187 n_entries = dtl_buf_entries;
188 buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
189 if (!buf) {
190 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
191 __func__, dtl->cpu);
192 read_unlock(&dtl_access_lock);
193 return -ENOMEM;
194 }
195
196 spin_lock(&dtl->lock);
197 rc = -EBUSY;
198 if (!dtl->buf) {
199 /* store the original allocation size for use during read */
200 dtl->buf_entries = n_entries;
201 dtl->buf = buf;
202 dtl->last_idx = 0;
203 rc = dtl_start(dtl);
204 if (rc)
205 dtl->buf = NULL;
206 }
207 spin_unlock(&dtl->lock);
208
209 if (rc) {
210 read_unlock(&dtl_access_lock);
211 kmem_cache_free(dtl_cache, buf);
212 }
213
214 return rc;
215 }
216
dtl_disable(struct dtl * dtl)217 static void dtl_disable(struct dtl *dtl)
218 {
219 spin_lock(&dtl->lock);
220 dtl_stop(dtl);
221 kmem_cache_free(dtl_cache, dtl->buf);
222 dtl->buf = NULL;
223 dtl->buf_entries = 0;
224 spin_unlock(&dtl->lock);
225 read_unlock(&dtl_access_lock);
226 }
227
228 /* file interface */
229
dtl_file_open(struct inode * inode,struct file * filp)230 static int dtl_file_open(struct inode *inode, struct file *filp)
231 {
232 struct dtl *dtl = inode->i_private;
233 int rc;
234
235 rc = dtl_enable(dtl);
236 if (rc)
237 return rc;
238
239 filp->private_data = dtl;
240 return 0;
241 }
242
dtl_file_release(struct inode * inode,struct file * filp)243 static int dtl_file_release(struct inode *inode, struct file *filp)
244 {
245 struct dtl *dtl = inode->i_private;
246 dtl_disable(dtl);
247 return 0;
248 }
249
dtl_file_read(struct file * filp,char __user * buf,size_t len,loff_t * pos)250 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
251 loff_t *pos)
252 {
253 long int rc, n_read, n_req, read_size;
254 struct dtl *dtl;
255 u64 cur_idx, last_idx, i;
256
257 if ((len % sizeof(struct dtl_entry)) != 0)
258 return -EINVAL;
259
260 dtl = filp->private_data;
261
262 /* requested number of entries to read */
263 n_req = len / sizeof(struct dtl_entry);
264
265 /* actual number of entries read */
266 n_read = 0;
267
268 spin_lock(&dtl->lock);
269
270 cur_idx = dtl_current_index(dtl);
271 last_idx = dtl->last_idx;
272
273 if (last_idx + dtl->buf_entries <= cur_idx)
274 last_idx = cur_idx - dtl->buf_entries + 1;
275
276 if (last_idx + n_req > cur_idx)
277 n_req = cur_idx - last_idx;
278
279 if (n_req > 0)
280 dtl->last_idx = last_idx + n_req;
281
282 spin_unlock(&dtl->lock);
283
284 if (n_req <= 0)
285 return 0;
286
287 i = last_idx % dtl->buf_entries;
288
289 /* read the tail of the buffer if we've wrapped */
290 if (i + n_req > dtl->buf_entries) {
291 read_size = dtl->buf_entries - i;
292
293 rc = copy_to_user(buf, &dtl->buf[i],
294 read_size * sizeof(struct dtl_entry));
295 if (rc)
296 return -EFAULT;
297
298 i = 0;
299 n_req -= read_size;
300 n_read += read_size;
301 buf += read_size * sizeof(struct dtl_entry);
302 }
303
304 /* .. and now the head */
305 rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
306 if (rc)
307 return -EFAULT;
308
309 n_read += n_req;
310
311 return n_read * sizeof(struct dtl_entry);
312 }
313
314 static const struct file_operations dtl_fops = {
315 .open = dtl_file_open,
316 .release = dtl_file_release,
317 .read = dtl_file_read,
318 .llseek = no_llseek,
319 };
320
321 static struct dentry *dtl_dir;
322
dtl_setup_file(struct dtl * dtl)323 static void dtl_setup_file(struct dtl *dtl)
324 {
325 char name[10];
326
327 sprintf(name, "cpu-%d", dtl->cpu);
328
329 debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
330 }
331
dtl_init(void)332 static int dtl_init(void)
333 {
334 int i;
335
336 if (!firmware_has_feature(FW_FEATURE_SPLPAR))
337 return -ENODEV;
338
339 /* set up common debugfs structure */
340
341 dtl_dir = debugfs_create_dir("dtl", arch_debugfs_dir);
342
343 debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
344 debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);
345
346 /* set up the per-cpu log structures */
347 for_each_possible_cpu(i) {
348 struct dtl *dtl = &per_cpu(cpu_dtl, i);
349 spin_lock_init(&dtl->lock);
350 dtl->cpu = i;
351
352 dtl_setup_file(dtl);
353 }
354
355 return 0;
356 }
357 machine_arch_initcall(pseries, dtl_init);
358