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