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
  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 = &__get_cpu_var(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 arch_initcall(dtl_init);