arch/powerpc/platforms/pseries/dtl.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Virtual Processor Dispatch Trace Log
   4  *
   5  * (C) Copyright IBM Corporation 2009
   6  *
   7  * Author: Jeremy Kerr <jk@ozlabs.org>
   8  */
   9
  10 #include <linux/slab.h>
  11 #include <linux/spinlock.h>
  12 #include <asm/smp.h>
  13 #include <linux/uaccess.h>
  14 #include <asm/firmware.h>
  15 #include <asm/dtl.h>
  16 #include <asm/lppaca.h>
  17 #include <asm/debugfs.h>
  18 #include <asm/plpar_wrappers.h>
  19 #include <asm/machdep.h>
  20
  21 struct dtl {
  22         struct dtl_entry        *buf;
  23         int                     cpu;
  24         int                     buf_entries;
  25         u64                     last_idx;
  26         spinlock_t              lock;
  27 };
  28 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
  29
  30 static u8 dtl_event_mask = DTL_LOG_ALL;
  31
  32
  33 /*
  34  * Size of per-cpu log buffers. Firmware requires that the buffer does
  35  * not cross a 4k boundary.
  36  */
  37 static int dtl_buf_entries = N_DISPATCH_LOG;
  38
  39 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
  40 struct dtl_ring {
  41         u64     write_index;
  42         struct dtl_entry *write_ptr;
  43         struct dtl_entry *buf;
  44         struct dtl_entry *buf_end;
  45 };
  46
  47 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
  48
  49 static atomic_t dtl_count;
  50
  51 /*
  52  * The cpu accounting code controls the DTL ring buffer, and we get
  53  * given entries as they are processed.
  54  */
  55 static void consume_dtle(struct dtl_entry *dtle, u64 index)
  56 {
  57         struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
  58         struct dtl_entry *wp = dtlr->write_ptr;
  59         struct lppaca *vpa = local_paca->lppaca_ptr;
  60
  61         if (!wp)
  62                 return;
  63
  64         *wp = *dtle;
  65         barrier();
  66
  67         /* check for hypervisor ring buffer overflow, ignore this entry if so */
  68         if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
  69                 return;
  70
  71         ++wp;
  72         if (wp == dtlr->buf_end)
  73                 wp = dtlr->buf;
  74         dtlr->write_ptr = wp;
  75
  76         /* incrementing write_index makes the new entry visible */
  77         smp_wmb();
  78         ++dtlr->write_index;
  79 }
  80
  81 static int dtl_start(struct dtl *dtl)
  82 {
  83         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
  84
  85         dtlr->buf = dtl->buf;
  86         dtlr->buf_end = dtl->buf + dtl->buf_entries;
  87         dtlr->write_index = 0;
  88
  89         /* setting write_ptr enables logging into our buffer */
  90         smp_wmb();
  91         dtlr->write_ptr = dtl->buf;
  92
  93         /* enable event logging */
  94         lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
  95
  96         dtl_consumer = consume_dtle;
  97         atomic_inc(&dtl_count);
  98         return 0;
  99 }
 100
 101 static void dtl_stop(struct dtl *dtl)
 102 {
 103         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
 104
 105         dtlr->write_ptr = NULL;
 106         smp_wmb();
 107
 108         dtlr->buf = NULL;
 109
 110         /* restore dtl_enable_mask */
 111         lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
 112
 113         if (atomic_dec_and_test(&dtl_count))
 114                 dtl_consumer = NULL;
 115 }
 116
 117 static u64 dtl_current_index(struct dtl *dtl)
 118 {
 119         return per_cpu(dtl_rings, dtl->cpu).write_index;
 120 }
 121
 122 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
 123
 124 static int dtl_start(struct dtl *dtl)
 125 {
 126         unsigned long addr;
 127         int ret, hwcpu;
 128
 129         /* Register our dtl buffer with the hypervisor. The HV expects the
 130          * buffer size to be passed in the second word of the buffer */
 131         ((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);
 132
 133         hwcpu = get_hard_smp_processor_id(dtl->cpu);
 134         addr = __pa(dtl->buf);
 135         ret = register_dtl(hwcpu, addr);
 136         if (ret) {
 137                 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
 138                        "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
 139                 return -EIO;
 140         }
 141
 142         /* set our initial buffer indices */
 143         lppaca_of(dtl->cpu).dtl_idx = 0;
 144
 145         /* ensure that our updates to the lppaca fields have occurred before
 146          * we actually enable the logging */
 147         smp_wmb();
 148
 149         /* enable event logging */
 150         lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
 151
 152         return 0;
 153 }
 154
 155 static void dtl_stop(struct dtl *dtl)
 156 {
 157         int hwcpu = get_hard_smp_processor_id(dtl->cpu);
 158
 159         lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
 160
 161         unregister_dtl(hwcpu);
 162 }
 163
 164 static u64 dtl_current_index(struct dtl *dtl)
 165 {
 166         return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
 167 }
 168 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
 169
 170 static int dtl_enable(struct dtl *dtl)
 171 {
 172         long int n_entries;
 173         long int rc;
 174         struct dtl_entry *buf = NULL;
 175
 176         if (!dtl_cache)
 177                 return -ENOMEM;
 178
 179         /* only allow one reader */
 180         if (dtl->buf)
 181                 return -EBUSY;
 182
 183         /* ensure there are no other conflicting dtl users */
 184         if (!read_trylock(&dtl_access_lock))
 185                 return -EBUSY;
 186
 187         n_entries = dtl_buf_entries;
 188         buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
 189         if (!buf) {
 190                 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
 191                                 __func__, dtl->cpu);
 192                 read_unlock(&dtl_access_lock);
 193                 return -ENOMEM;
 194         }
 195
 196         spin_lock(&dtl->lock);
 197         rc = -EBUSY;
 198         if (!dtl->buf) {
 199                 /* store the original allocation size for use during read */
 200                 dtl->buf_entries = n_entries;
 201                 dtl->buf = buf;
 202                 dtl->last_idx = 0;
 203                 rc = dtl_start(dtl);
 204                 if (rc)
 205                         dtl->buf = NULL;
 206         }
 207         spin_unlock(&dtl->lock);
 208
 209         if (rc) {
 210                 read_unlock(&dtl_access_lock);
 211                 kmem_cache_free(dtl_cache, buf);
 212         }
 213
 214         return rc;
 215 }
 216
 217 static void dtl_disable(struct dtl *dtl)
 218 {
 219         spin_lock(&dtl->lock);
 220         dtl_stop(dtl);
 221         kmem_cache_free(dtl_cache, dtl->buf);
 222         dtl->buf = NULL;
 223         dtl->buf_entries = 0;
 224         spin_unlock(&dtl->lock);
 225         read_unlock(&dtl_access_lock);
 226 }
 227
 228 /* file interface */
 229
 230 static int dtl_file_open(struct inode *inode, struct file *filp)
 231 {
 232         struct dtl *dtl = inode->i_private;
 233         int rc;
 234
 235         rc = dtl_enable(dtl);
 236         if (rc)
 237                 return rc;
 238
 239         filp->private_data = dtl;
 240         return 0;
 241 }
 242
 243 static int dtl_file_release(struct inode *inode, struct file *filp)
 244 {
 245         struct dtl *dtl = inode->i_private;
 246         dtl_disable(dtl);
 247         return 0;
 248 }
 249
 250 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
 251                 loff_t *pos)
 252 {
 253         long int rc, n_read, n_req, read_size;
 254         struct dtl *dtl;
 255         u64 cur_idx, last_idx, i;
 256
 257         if ((len % sizeof(struct dtl_entry)) != 0)
 258                 return -EINVAL;
 259
 260         dtl = filp->private_data;
 261
 262         /* requested number of entries to read */
 263         n_req = len / sizeof(struct dtl_entry);
 264
 265         /* actual number of entries read */
 266         n_read = 0;
 267
 268         spin_lock(&dtl->lock);
 269
 270         cur_idx = dtl_current_index(dtl);
 271         last_idx = dtl->last_idx;
 272
 273         if (last_idx + dtl->buf_entries <= cur_idx)
 274                 last_idx = cur_idx - dtl->buf_entries + 1;
 275
 276         if (last_idx + n_req > cur_idx)
 277                 n_req = cur_idx - last_idx;
 278
 279         if (n_req > 0)
 280                 dtl->last_idx = last_idx + n_req;
 281
 282         spin_unlock(&dtl->lock);
 283
 284         if (n_req <= 0)
 285                 return 0;
 286
 287         i = last_idx % dtl->buf_entries;
 288
 289         /* read the tail of the buffer if we've wrapped */
 290         if (i + n_req > dtl->buf_entries) {
 291                 read_size = dtl->buf_entries - i;
 292
 293                 rc = copy_to_user(buf, &dtl->buf[i],
 294                                 read_size * sizeof(struct dtl_entry));
 295                 if (rc)
 296                         return -EFAULT;
 297
 298                 i = 0;
 299                 n_req -= read_size;
 300                 n_read += read_size;
 301                 buf += read_size * sizeof(struct dtl_entry);
 302         }
 303
 304         /* .. and now the head */
 305         rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
 306         if (rc)
 307                 return -EFAULT;
 308
 309         n_read += n_req;
 310
 311         return n_read * sizeof(struct dtl_entry);
 312 }
 313
 314 static const struct file_operations dtl_fops = {
 315         .open           = dtl_file_open,
 316         .release        = dtl_file_release,
 317         .read           = dtl_file_read,
 318         .llseek         = no_llseek,
 319 };
 320
 321 static struct dentry *dtl_dir;
 322
 323 static void dtl_setup_file(struct dtl *dtl)
 324 {
 325         char name[10];
 326
 327         sprintf(name, "cpu-%d", dtl->cpu);
 328
 329         debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
 330 }
 331
 332 static int dtl_init(void)
 333 {
 334         int i;
 335
 336         if (!firmware_has_feature(FW_FEATURE_SPLPAR))
 337                 return -ENODEV;
 338
 339         /* set up common debugfs structure */
 340
 341         dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
 342
 343         debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
 344         debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);
 345
 346         /* set up the per-cpu log structures */
 347         for_each_possible_cpu(i) {
 348                 struct dtl *dtl = &per_cpu(cpu_dtl, i);
 349                 spin_lock_init(&dtl->lock);
 350                 dtl->cpu = i;
 351
 352                 dtl_setup_file(dtl);
 353         }
 354
 355         return 0;
 356 }
 357 machine_arch_initcall(pseries, dtl_init);