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/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 static u8 dtl_event_mask = DTL_LOG_ALL;
  44
  45
  46 /*
  47  * Size of per-cpu log buffers. Firmware requires that the buffer does
  48  * not cross a 4k boundary.
  49  */
  50 static int dtl_buf_entries = N_DISPATCH_LOG;
  51
  52 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
  53 struct dtl_ring {
  54         u64     write_index;
  55         struct dtl_entry *write_ptr;
  56         struct dtl_entry *buf;
  57         struct dtl_entry *buf_end;
  58 };
  59
  60 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
  61
  62 static atomic_t dtl_count;
  63
  64 /*
  65  * The cpu accounting code controls the DTL ring buffer, and we get
  66  * given entries as they are processed.
  67  */
  68 static void consume_dtle(struct dtl_entry *dtle, u64 index)
  69 {
  70         struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
  71         struct dtl_entry *wp = dtlr->write_ptr;
  72         struct lppaca *vpa = local_paca->lppaca_ptr;
  73
  74         if (!wp)
  75                 return;
  76
  77         *wp = *dtle;
  78         barrier();
  79
  80         /* check for hypervisor ring buffer overflow, ignore this entry if so */
  81         if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
  82                 return;
  83
  84         ++wp;
  85         if (wp == dtlr->buf_end)
  86                 wp = dtlr->buf;
  87         dtlr->write_ptr = wp;
  88
  89         /* incrementing write_index makes the new entry visible */
  90         smp_wmb();
  91         ++dtlr->write_index;
  92 }
  93
  94 static int dtl_start(struct dtl *dtl)
  95 {
  96         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
  97
  98         dtlr->buf = dtl->buf;
  99         dtlr->buf_end = dtl->buf + dtl->buf_entries;
 100         dtlr->write_index = 0;
 101
 102         /* setting write_ptr enables logging into our buffer */
 103         smp_wmb();
 104         dtlr->write_ptr = dtl->buf;
 105
 106         /* enable event logging */
 107         lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
 108
 109         dtl_consumer = consume_dtle;
 110         atomic_inc(&dtl_count);
 111         return 0;
 112 }
 113
 114 static void dtl_stop(struct dtl *dtl)
 115 {
 116         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
 117
 118         dtlr->write_ptr = NULL;
 119         smp_wmb();
 120
 121         dtlr->buf = NULL;
 122
 123         /* restore dtl_enable_mask */
 124         lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
 125
 126         if (atomic_dec_and_test(&dtl_count))
 127                 dtl_consumer = NULL;
 128 }
 129
 130 static u64 dtl_current_index(struct dtl *dtl)
 131 {
 132         return per_cpu(dtl_rings, dtl->cpu).write_index;
 133 }
 134
 135 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
 136
 137 static int dtl_start(struct dtl *dtl)
 138 {
 139         unsigned long addr;
 140         int ret, hwcpu;
 141
 142         /* Register our dtl buffer with the hypervisor. The HV expects the
 143          * buffer size to be passed in the second word of the buffer */
 144         ((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);
 145
 146         hwcpu = get_hard_smp_processor_id(dtl->cpu);
 147         addr = __pa(dtl->buf);
 148         ret = register_dtl(hwcpu, addr);
 149         if (ret) {
 150                 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
 151                        "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
 152                 return -EIO;
 153         }
 154
 155         /* set our initial buffer indices */
 156         lppaca_of(dtl->cpu).dtl_idx = 0;
 157
 158         /* ensure that our updates to the lppaca fields have occurred before
 159          * we actually enable the logging */
 160         smp_wmb();
 161
 162         /* enable event logging */
 163         lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
 164
 165         return 0;
 166 }
 167
 168 static void dtl_stop(struct dtl *dtl)
 169 {
 170         int hwcpu = get_hard_smp_processor_id(dtl->cpu);
 171
 172         lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
 173
 174         unregister_dtl(hwcpu);
 175 }
 176
 177 static u64 dtl_current_index(struct dtl *dtl)
 178 {
 179         return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
 180 }
 181 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
 182
 183 static int dtl_enable(struct dtl *dtl)
 184 {
 185         long int n_entries;
 186         long int rc;
 187         struct dtl_entry *buf = NULL;
 188
 189         if (!dtl_cache)
 190                 return -ENOMEM;
 191
 192         /* only allow one reader */
 193         if (dtl->buf)
 194                 return -EBUSY;
 195
 196         n_entries = dtl_buf_entries;
 197         buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
 198         if (!buf) {
 199                 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
 200                                 __func__, dtl->cpu);
 201                 return -ENOMEM;
 202         }
 203
 204         spin_lock(&dtl->lock);
 205         rc = -EBUSY;
 206         if (!dtl->buf) {
 207                 /* store the original allocation size for use during read */
 208                 dtl->buf_entries = n_entries;
 209                 dtl->buf = buf;
 210                 dtl->last_idx = 0;
 211                 rc = dtl_start(dtl);
 212                 if (rc)
 213                         dtl->buf = NULL;
 214         }
 215         spin_unlock(&dtl->lock);
 216
 217         if (rc)
 218                 kmem_cache_free(dtl_cache, buf);
 219         return rc;
 220 }
 221
 222 static void dtl_disable(struct dtl *dtl)
 223 {
 224         spin_lock(&dtl->lock);
 225         dtl_stop(dtl);
 226         kmem_cache_free(dtl_cache, dtl->buf);
 227         dtl->buf = NULL;
 228         dtl->buf_entries = 0;
 229         spin_unlock(&dtl->lock);
 230 }
 231
 232 /* file interface */
 233
 234 static int dtl_file_open(struct inode *inode, struct file *filp)
 235 {
 236         struct dtl *dtl = inode->i_private;
 237         int rc;
 238
 239         rc = dtl_enable(dtl);
 240         if (rc)
 241                 return rc;
 242
 243         filp->private_data = dtl;
 244         return 0;
 245 }
 246
 247 static int dtl_file_release(struct inode *inode, struct file *filp)
 248 {
 249         struct dtl *dtl = inode->i_private;
 250         dtl_disable(dtl);
 251         return 0;
 252 }
 253
 254 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
 255                 loff_t *pos)
 256 {
 257         long int rc, n_read, n_req, read_size;
 258         struct dtl *dtl;
 259         u64 cur_idx, last_idx, i;
 260
 261         if ((len % sizeof(struct dtl_entry)) != 0)
 262                 return -EINVAL;
 263
 264         dtl = filp->private_data;
 265
 266         /* requested number of entries to read */
 267         n_req = len / sizeof(struct dtl_entry);
 268
 269         /* actual number of entries read */
 270         n_read = 0;
 271
 272         spin_lock(&dtl->lock);
 273
 274         cur_idx = dtl_current_index(dtl);
 275         last_idx = dtl->last_idx;
 276
 277         if (last_idx + dtl->buf_entries <= cur_idx)
 278                 last_idx = cur_idx - dtl->buf_entries + 1;
 279
 280         if (last_idx + n_req > cur_idx)
 281                 n_req = cur_idx - last_idx;
 282
 283         if (n_req > 0)
 284                 dtl->last_idx = last_idx + n_req;
 285
 286         spin_unlock(&dtl->lock);
 287
 288         if (n_req <= 0)
 289                 return 0;
 290
 291         i = last_idx % dtl->buf_entries;
 292
 293         /* read the tail of the buffer if we've wrapped */
 294         if (i + n_req > dtl->buf_entries) {
 295                 read_size = dtl->buf_entries - i;
 296
 297                 rc = copy_to_user(buf, &dtl->buf[i],
 298                                 read_size * sizeof(struct dtl_entry));
 299                 if (rc)
 300                         return -EFAULT;
 301
 302                 i = 0;
 303                 n_req -= read_size;
 304                 n_read += read_size;
 305                 buf += read_size * sizeof(struct dtl_entry);
 306         }
 307
 308         /* .. and now the head */
 309         rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
 310         if (rc)
 311                 return -EFAULT;
 312
 313         n_read += n_req;
 314
 315         return n_read * sizeof(struct dtl_entry);
 316 }
 317
 318 static const struct file_operations dtl_fops = {
 319         .open           = dtl_file_open,
 320         .release        = dtl_file_release,
 321         .read           = dtl_file_read,
 322         .llseek         = no_llseek,
 323 };
 324
 325 static struct dentry *dtl_dir;
 326
 327 static int dtl_setup_file(struct dtl *dtl)
 328 {
 329         char name[10];
 330
 331         sprintf(name, "cpu-%d", dtl->cpu);
 332
 333         dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
 334         if (!dtl->file)
 335                 return -ENOMEM;
 336
 337         return 0;
 338 }
 339
 340 static int dtl_init(void)
 341 {
 342         struct dentry *event_mask_file, *buf_entries_file;
 343         int rc, i;
 344
 345         if (!firmware_has_feature(FW_FEATURE_SPLPAR))
 346                 return -ENODEV;
 347
 348         /* set up common debugfs structure */
 349
 350         rc = -ENOMEM;
 351         dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
 352         if (!dtl_dir) {
 353                 printk(KERN_WARNING "%s: can't create dtl root dir\n",
 354                                 __func__);
 355                 goto err;
 356         }
 357
 358         event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
 359                                 dtl_dir, &dtl_event_mask);
 360         buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0400,
 361                                 dtl_dir, &dtl_buf_entries);
 362
 363         if (!event_mask_file || !buf_entries_file) {
 364                 printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
 365                 goto err_remove_dir;
 366         }
 367
 368         /* set up the per-cpu log structures */
 369         for_each_possible_cpu(i) {
 370                 struct dtl *dtl = &per_cpu(cpu_dtl, i);
 371                 spin_lock_init(&dtl->lock);
 372                 dtl->cpu = i;
 373
 374                 rc = dtl_setup_file(dtl);
 375                 if (rc)
 376                         goto err_remove_dir;
 377         }
 378
 379         return 0;
 380
 381 err_remove_dir:
 382         debugfs_remove_recursive(dtl_dir);
 383 err:
 384         return rc;
 385 }
 386 machine_arch_initcall(pseries, dtl_init);