arch/powerpc/platforms/pseries/dtl.c

   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);