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  */
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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