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