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