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/debugfs.h>
  25 #include <asm/smp.h>
  26 #include <asm/system.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/firmware.h>
  29
  30 #include "plpar_wrappers.h"
  31
  32 /*
  33  * Layout of entries in the hypervisor's DTL buffer. Although we don't
  34  * actually access the internals of an entry (we only need to know the size),
  35  * we might as well define it here for reference.
  36  */
  37 struct dtl_entry {
  38         u8      dispatch_reason;
  39         u8      preempt_reason;
  40         u16     processor_id;
  41         u32     enqueue_to_dispatch_time;
  42         u32     ready_to_enqueue_time;
  43         u32     waiting_to_ready_time;
  44         u64     timebase;
  45         u64     fault_addr;
  46         u64     srr0;
  47         u64     srr1;
  48 };
  49
  50 struct dtl {
  51         struct dtl_entry        *buf;
  52         struct dentry           *file;
  53         int                     cpu;
  54         int                     buf_entries;
  55         u64                     last_idx;
  56 };
  57 static DEFINE_PER_CPU(struct dtl, dtl);
  58
  59 /*
  60  * Dispatch trace log event mask:
  61  * 0x7: 0x1: voluntary virtual processor waits
  62  *      0x2: time-slice preempts
  63  *      0x4: virtual partition memory page faults
  64  */
  65 static u8 dtl_event_mask = 0x7;
  66
  67
  68 /*
  69  * Size of per-cpu log buffers. Default is just under 16 pages worth.
  70  */
  71 static int dtl_buf_entries = (16 * 85);
  72
  73
  74 static int dtl_enable(struct dtl *dtl)
  75 {
  76         unsigned long addr;
  77         int ret, hwcpu;
  78
  79         /* only allow one reader */
  80         if (dtl->buf)
  81                 return -EBUSY;
  82
  83         /* we need to store the original allocation size for use during read */
  84         dtl->buf_entries = dtl_buf_entries;
  85
  86         dtl->buf = kmalloc_node(dtl->buf_entries * sizeof(struct dtl_entry),
  87                         GFP_KERNEL, cpu_to_node(dtl->cpu));
  88         if (!dtl->buf) {
  89                 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
  90                                 __func__, dtl->cpu);
  91                 return -ENOMEM;
  92         }
  93
  94         /* Register our dtl buffer with the hypervisor. The HV expects the
  95          * buffer size to be passed in the second word of the buffer */
  96         ((u32 *)dtl->buf)[1] = dtl->buf_entries * sizeof(struct dtl_entry);
  97
  98         hwcpu = get_hard_smp_processor_id(dtl->cpu);
  99         addr = __pa(dtl->buf);
 100         ret = register_dtl(hwcpu, addr);
 101         if (ret) {
 102                 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
 103                        "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
 104                 kfree(dtl->buf);
 105                 return -EIO;
 106         }
 107
 108         /* set our initial buffer indices */
 109         dtl->last_idx = lppaca[dtl->cpu].dtl_idx = 0;
 110
 111         /* ensure that our updates to the lppaca fields have occurred before
 112          * we actually enable the logging */
 113         smp_wmb();
 114
 115         /* enable event logging */
 116         lppaca[dtl->cpu].dtl_enable_mask = dtl_event_mask;
 117
 118         return 0;
 119 }
 120
 121 static void dtl_disable(struct dtl *dtl)
 122 {
 123         int hwcpu = get_hard_smp_processor_id(dtl->cpu);
 124
 125         lppaca[dtl->cpu].dtl_enable_mask = 0x0;
 126
 127         unregister_dtl(hwcpu, __pa(dtl->buf));
 128
 129         kfree(dtl->buf);
 130         dtl->buf = NULL;
 131         dtl->buf_entries = 0;
 132 }
 133
 134 /* file interface */
 135
 136 static int dtl_file_open(struct inode *inode, struct file *filp)
 137 {
 138         struct dtl *dtl = inode->i_private;
 139         int rc;
 140
 141         rc = dtl_enable(dtl);
 142         if (rc)
 143                 return rc;
 144
 145         filp->private_data = dtl;
 146         return 0;
 147 }
 148
 149 static int dtl_file_release(struct inode *inode, struct file *filp)
 150 {
 151         struct dtl *dtl = inode->i_private;
 152         dtl_disable(dtl);
 153         return 0;
 154 }
 155
 156 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
 157                 loff_t *pos)
 158 {
 159         int rc, cur_idx, last_idx, n_read, n_req, read_size;
 160         struct dtl *dtl;
 161
 162         if ((len % sizeof(struct dtl_entry)) != 0)
 163                 return -EINVAL;
 164
 165         dtl = filp->private_data;
 166
 167         /* requested number of entries to read */
 168         n_req = len / sizeof(struct dtl_entry);
 169
 170         /* actual number of entries read */
 171         n_read = 0;
 172
 173         cur_idx = lppaca[dtl->cpu].dtl_idx;
 174         last_idx = dtl->last_idx;
 175
 176         if (cur_idx - last_idx > dtl->buf_entries) {
 177                 pr_debug("%s: hv buffer overflow for cpu %d, samples lost\n",
 178                                 __func__, dtl->cpu);
 179         }
 180
 181         cur_idx  %= dtl->buf_entries;
 182         last_idx %= dtl->buf_entries;
 183
 184         /* read the tail of the buffer if we've wrapped */
 185         if (last_idx > cur_idx) {
 186                 read_size = min(n_req, dtl->buf_entries - last_idx);
 187
 188                 rc = copy_to_user(buf, &dtl->buf[last_idx],
 189                                 read_size * sizeof(struct dtl_entry));
 190                 if (rc)
 191                         return -EFAULT;
 192
 193                 last_idx = 0;
 194                 n_req -= read_size;
 195                 n_read += read_size;
 196                 buf += read_size * sizeof(struct dtl_entry);
 197         }
 198
 199         /* .. and now the head */
 200         read_size = min(n_req, cur_idx - last_idx);
 201         rc = copy_to_user(buf, &dtl->buf[last_idx],
 202                         read_size * sizeof(struct dtl_entry));
 203         if (rc)
 204                 return -EFAULT;
 205
 206         n_read += read_size;
 207         dtl->last_idx += n_read;
 208
 209         return n_read * sizeof(struct dtl_entry);
 210 }
 211
 212 static struct file_operations dtl_fops = {
 213         .open           = dtl_file_open,
 214         .release        = dtl_file_release,
 215         .read           = dtl_file_read,
 216         .llseek         = no_llseek,
 217 };
 218
 219 static struct dentry *dtl_dir;
 220
 221 static int dtl_setup_file(struct dtl *dtl)
 222 {
 223         char name[10];
 224
 225         sprintf(name, "cpu-%d", dtl->cpu);
 226
 227         dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
 228         if (!dtl->file)
 229                 return -ENOMEM;
 230
 231         return 0;
 232 }
 233
 234 static int dtl_init(void)
 235 {
 236         struct dentry *event_mask_file, *buf_entries_file;
 237         int rc, i;
 238
 239         if (!firmware_has_feature(FW_FEATURE_SPLPAR))
 240                 return -ENODEV;
 241
 242         /* set up common debugfs structure */
 243
 244         rc = -ENOMEM;
 245         dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
 246         if (!dtl_dir) {
 247                 printk(KERN_WARNING "%s: can't create dtl root dir\n",
 248                                 __func__);
 249                 goto err;
 250         }
 251
 252         event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
 253                                 dtl_dir, &dtl_event_mask);
 254         buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0600,
 255                                 dtl_dir, &dtl_buf_entries);
 256
 257         if (!event_mask_file || !buf_entries_file) {
 258                 printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
 259                 goto err_remove_dir;
 260         }
 261
 262         /* set up the per-cpu log structures */
 263         for_each_possible_cpu(i) {
 264                 struct dtl *dtl = &per_cpu(dtl, i);
 265                 dtl->cpu = i;
 266
 267                 rc = dtl_setup_file(dtl);
 268                 if (rc)
 269                         goto err_remove_dir;
 270         }
 271
 272         return 0;
 273
 274 err_remove_dir:
 275         debugfs_remove_recursive(dtl_dir);
 276 err:
 277         return rc;
 278 }
 279 arch_initcall(dtl_init);