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