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