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Linux/arch/powerpc/platforms/pseries/dtl.c

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  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/slab.h>
 24 #include <linux/debugfs.h>
 25 #include <linux/spinlock.h>
 26 #include <asm/smp.h>
 27 #include <asm/uaccess.h>
 28 #include <asm/firmware.h>
 29 #include <asm/lppaca.h>
 30 #include <asm/debug.h>
 31 #include <asm/plpar_wrappers.h>
 32 #include <asm/machdep.h>
 33 
 34 struct dtl {
 35         struct dtl_entry        *buf;
 36         struct dentry           *file;
 37         int                     cpu;
 38         int                     buf_entries;
 39         u64                     last_idx;
 40         spinlock_t              lock;
 41 };
 42 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
 43 
 44 /*
 45  * Dispatch trace log event mask:
 46  * 0x7: 0x1: voluntary virtual processor waits
 47  *      0x2: time-slice preempts
 48  *      0x4: virtual partition memory page faults
 49  */
 50 static u8 dtl_event_mask = 0x7;
 51 
 52 
 53 /*
 54  * Size of per-cpu log buffers. Firmware requires that the buffer does
 55  * not cross a 4k boundary.
 56  */
 57 static int dtl_buf_entries = N_DISPATCH_LOG;
 58 
 59 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
 60 struct dtl_ring {
 61         u64     write_index;
 62         struct dtl_entry *write_ptr;
 63         struct dtl_entry *buf;
 64         struct dtl_entry *buf_end;
 65         u8      saved_dtl_mask;
 66 };
 67 
 68 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
 69 
 70 static atomic_t dtl_count;
 71 
 72 /*
 73  * The cpu accounting code controls the DTL ring buffer, and we get
 74  * given entries as they are processed.
 75  */
 76 static void consume_dtle(struct dtl_entry *dtle, u64 index)
 77 {
 78         struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
 79         struct dtl_entry *wp = dtlr->write_ptr;
 80         struct lppaca *vpa = local_paca->lppaca_ptr;
 81 
 82         if (!wp)
 83                 return;
 84 
 85         *wp = *dtle;
 86         barrier();
 87 
 88         /* check for hypervisor ring buffer overflow, ignore this entry if so */
 89         if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
 90                 return;
 91 
 92         ++wp;
 93         if (wp == dtlr->buf_end)
 94                 wp = dtlr->buf;
 95         dtlr->write_ptr = wp;
 96 
 97         /* incrementing write_index makes the new entry visible */
 98         smp_wmb();
 99         ++dtlr->write_index;
100 }
101 
102 static int dtl_start(struct dtl *dtl)
103 {
104         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
105 
106         dtlr->buf = dtl->buf;
107         dtlr->buf_end = dtl->buf + dtl->buf_entries;
108         dtlr->write_index = 0;
109 
110         /* setting write_ptr enables logging into our buffer */
111         smp_wmb();
112         dtlr->write_ptr = dtl->buf;
113 
114         /* enable event logging */
115         dtlr->saved_dtl_mask = lppaca_of(dtl->cpu).dtl_enable_mask;
116         lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
117 
118         dtl_consumer = consume_dtle;
119         atomic_inc(&dtl_count);
120         return 0;
121 }
122 
123 static void dtl_stop(struct dtl *dtl)
124 {
125         struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
126 
127         dtlr->write_ptr = NULL;
128         smp_wmb();
129 
130         dtlr->buf = NULL;
131 
132         /* restore dtl_enable_mask */
133         lppaca_of(dtl->cpu).dtl_enable_mask = dtlr->saved_dtl_mask;
134 
135         if (atomic_dec_and_test(&dtl_count))
136                 dtl_consumer = NULL;
137 }
138 
139 static u64 dtl_current_index(struct dtl *dtl)
140 {
141         return per_cpu(dtl_rings, dtl->cpu).write_index;
142 }
143 
144 #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
145 
146 static int dtl_start(struct dtl *dtl)
147 {
148         unsigned long addr;
149         int ret, hwcpu;
150 
151         /* Register our dtl buffer with the hypervisor. The HV expects the
152          * buffer size to be passed in the second word of the buffer */
153         ((u32 *)dtl->buf)[1] = DISPATCH_LOG_BYTES;
154 
155         hwcpu = get_hard_smp_processor_id(dtl->cpu);
156         addr = __pa(dtl->buf);
157         ret = register_dtl(hwcpu, addr);
158         if (ret) {
159                 printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
160                        "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
161                 return -EIO;
162         }
163 
164         /* set our initial buffer indices */
165         lppaca_of(dtl->cpu).dtl_idx = 0;
166 
167         /* ensure that our updates to the lppaca fields have occurred before
168          * we actually enable the logging */
169         smp_wmb();
170 
171         /* enable event logging */
172         lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
173 
174         return 0;
175 }
176 
177 static void dtl_stop(struct dtl *dtl)
178 {
179         int hwcpu = get_hard_smp_processor_id(dtl->cpu);
180 
181         lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
182 
183         unregister_dtl(hwcpu);
184 }
185 
186 static u64 dtl_current_index(struct dtl *dtl)
187 {
188         return lppaca_of(dtl->cpu).dtl_idx;
189 }
190 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
191 
192 static int dtl_enable(struct dtl *dtl)
193 {
194         long int n_entries;
195         long int rc;
196         struct dtl_entry *buf = NULL;
197 
198         if (!dtl_cache)
199                 return -ENOMEM;
200 
201         /* only allow one reader */
202         if (dtl->buf)
203                 return -EBUSY;
204 
205         n_entries = dtl_buf_entries;
206         buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
207         if (!buf) {
208                 printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
209                                 __func__, dtl->cpu);
210                 return -ENOMEM;
211         }
212 
213         spin_lock(&dtl->lock);
214         rc = -EBUSY;
215         if (!dtl->buf) {
216                 /* store the original allocation size for use during read */
217                 dtl->buf_entries = n_entries;
218                 dtl->buf = buf;
219                 dtl->last_idx = 0;
220                 rc = dtl_start(dtl);
221                 if (rc)
222                         dtl->buf = NULL;
223         }
224         spin_unlock(&dtl->lock);
225 
226         if (rc)
227                 kmem_cache_free(dtl_cache, buf);
228         return rc;
229 }
230 
231 static void dtl_disable(struct dtl *dtl)
232 {
233         spin_lock(&dtl->lock);
234         dtl_stop(dtl);
235         kmem_cache_free(dtl_cache, dtl->buf);
236         dtl->buf = NULL;
237         dtl->buf_entries = 0;
238         spin_unlock(&dtl->lock);
239 }
240 
241 /* file interface */
242 
243 static int dtl_file_open(struct inode *inode, struct file *filp)
244 {
245         struct dtl *dtl = inode->i_private;
246         int rc;
247 
248         rc = dtl_enable(dtl);
249         if (rc)
250                 return rc;
251 
252         filp->private_data = dtl;
253         return 0;
254 }
255 
256 static int dtl_file_release(struct inode *inode, struct file *filp)
257 {
258         struct dtl *dtl = inode->i_private;
259         dtl_disable(dtl);
260         return 0;
261 }
262 
263 static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
264                 loff_t *pos)
265 {
266         long int rc, n_read, n_req, read_size;
267         struct dtl *dtl;
268         u64 cur_idx, last_idx, i;
269 
270         if ((len % sizeof(struct dtl_entry)) != 0)
271                 return -EINVAL;
272 
273         dtl = filp->private_data;
274 
275         /* requested number of entries to read */
276         n_req = len / sizeof(struct dtl_entry);
277 
278         /* actual number of entries read */
279         n_read = 0;
280 
281         spin_lock(&dtl->lock);
282 
283         cur_idx = dtl_current_index(dtl);
284         last_idx = dtl->last_idx;
285 
286         if (last_idx + dtl->buf_entries <= cur_idx)
287                 last_idx = cur_idx - dtl->buf_entries + 1;
288 
289         if (last_idx + n_req > cur_idx)
290                 n_req = cur_idx - last_idx;
291 
292         if (n_req > 0)
293                 dtl->last_idx = last_idx + n_req;
294 
295         spin_unlock(&dtl->lock);
296 
297         if (n_req <= 0)
298                 return 0;
299 
300         i = last_idx % dtl->buf_entries;
301 
302         /* read the tail of the buffer if we've wrapped */
303         if (i + n_req > dtl->buf_entries) {
304                 read_size = dtl->buf_entries - i;
305 
306                 rc = copy_to_user(buf, &dtl->buf[i],
307                                 read_size * sizeof(struct dtl_entry));
308                 if (rc)
309                         return -EFAULT;
310 
311                 i = 0;
312                 n_req -= read_size;
313                 n_read += read_size;
314                 buf += read_size * sizeof(struct dtl_entry);
315         }
316 
317         /* .. and now the head */
318         rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
319         if (rc)
320                 return -EFAULT;
321 
322         n_read += n_req;
323 
324         return n_read * sizeof(struct dtl_entry);
325 }
326 
327 static const struct file_operations dtl_fops = {
328         .open           = dtl_file_open,
329         .release        = dtl_file_release,
330         .read           = dtl_file_read,
331         .llseek         = no_llseek,
332 };
333 
334 static struct dentry *dtl_dir;
335 
336 static int dtl_setup_file(struct dtl *dtl)
337 {
338         char name[10];
339 
340         sprintf(name, "cpu-%d", dtl->cpu);
341 
342         dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
343         if (!dtl->file)
344                 return -ENOMEM;
345 
346         return 0;
347 }
348 
349 static int dtl_init(void)
350 {
351         struct dentry *event_mask_file, *buf_entries_file;
352         int rc, i;
353 
354         if (!firmware_has_feature(FW_FEATURE_SPLPAR))
355                 return -ENODEV;
356 
357         /* set up common debugfs structure */
358 
359         rc = -ENOMEM;
360         dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
361         if (!dtl_dir) {
362                 printk(KERN_WARNING "%s: can't create dtl root dir\n",
363                                 __func__);
364                 goto err;
365         }
366 
367         event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
368                                 dtl_dir, &dtl_event_mask);
369         buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0400,
370                                 dtl_dir, &dtl_buf_entries);
371 
372         if (!event_mask_file || !buf_entries_file) {
373                 printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
374                 goto err_remove_dir;
375         }
376 
377         /* set up the per-cpu log structures */
378         for_each_possible_cpu(i) {
379                 struct dtl *dtl = &per_cpu(cpu_dtl, i);
380                 spin_lock_init(&dtl->lock);
381                 dtl->cpu = i;
382 
383                 rc = dtl_setup_file(dtl);
384                 if (rc)
385                         goto err_remove_dir;
386         }
387 
388         return 0;
389 
390 err_remove_dir:
391         debugfs_remove_recursive(dtl_dir);
392 err:
393         return rc;
394 }
395 machine_arch_initcall(pseries, dtl_init);
396 

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