xref: /openbmc/linux/drivers/virtio/virtio.c (revision caf58a2c)
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/virtio.h>
3 #include <linux/spinlock.h>
4 #include <linux/virtio_config.h>
5 #include <linux/module.h>
6 #include <linux/idr.h>
7 #include <uapi/linux/virtio_ids.h>
8 
9 /* Unique numbering for virtio devices. */
10 static DEFINE_IDA(virtio_index_ida);
11 
12 static ssize_t device_show(struct device *_d,
13 			   struct device_attribute *attr, char *buf)
14 {
15 	struct virtio_device *dev = dev_to_virtio(_d);
16 	return sprintf(buf, "0x%04x\n", dev->id.device);
17 }
18 static DEVICE_ATTR_RO(device);
19 
20 static ssize_t vendor_show(struct device *_d,
21 			   struct device_attribute *attr, char *buf)
22 {
23 	struct virtio_device *dev = dev_to_virtio(_d);
24 	return sprintf(buf, "0x%04x\n", dev->id.vendor);
25 }
26 static DEVICE_ATTR_RO(vendor);
27 
28 static ssize_t status_show(struct device *_d,
29 			   struct device_attribute *attr, char *buf)
30 {
31 	struct virtio_device *dev = dev_to_virtio(_d);
32 	return sprintf(buf, "0x%08x\n", dev->config->get_status(dev));
33 }
34 static DEVICE_ATTR_RO(status);
35 
36 static ssize_t modalias_show(struct device *_d,
37 			     struct device_attribute *attr, char *buf)
38 {
39 	struct virtio_device *dev = dev_to_virtio(_d);
40 	return sprintf(buf, "virtio:d%08Xv%08X\n",
41 		       dev->id.device, dev->id.vendor);
42 }
43 static DEVICE_ATTR_RO(modalias);
44 
45 static ssize_t features_show(struct device *_d,
46 			     struct device_attribute *attr, char *buf)
47 {
48 	struct virtio_device *dev = dev_to_virtio(_d);
49 	unsigned int i;
50 	ssize_t len = 0;
51 
52 	/* We actually represent this as a bitstring, as it could be
53 	 * arbitrary length in future. */
54 	for (i = 0; i < sizeof(dev->features)*8; i++)
55 		len += sprintf(buf+len, "%c",
56 			       __virtio_test_bit(dev, i) ? '1' : '0');
57 	len += sprintf(buf+len, "\n");
58 	return len;
59 }
60 static DEVICE_ATTR_RO(features);
61 
62 static struct attribute *virtio_dev_attrs[] = {
63 	&dev_attr_device.attr,
64 	&dev_attr_vendor.attr,
65 	&dev_attr_status.attr,
66 	&dev_attr_modalias.attr,
67 	&dev_attr_features.attr,
68 	NULL,
69 };
70 ATTRIBUTE_GROUPS(virtio_dev);
71 
72 static inline int virtio_id_match(const struct virtio_device *dev,
73 				  const struct virtio_device_id *id)
74 {
75 	if (id->device != dev->id.device && id->device != VIRTIO_DEV_ANY_ID)
76 		return 0;
77 
78 	return id->vendor == VIRTIO_DEV_ANY_ID || id->vendor == dev->id.vendor;
79 }
80 
81 /* This looks through all the IDs a driver claims to support.  If any of them
82  * match, we return 1 and the kernel will call virtio_dev_probe(). */
83 static int virtio_dev_match(struct device *_dv, struct device_driver *_dr)
84 {
85 	unsigned int i;
86 	struct virtio_device *dev = dev_to_virtio(_dv);
87 	const struct virtio_device_id *ids;
88 
89 	ids = drv_to_virtio(_dr)->id_table;
90 	for (i = 0; ids[i].device; i++)
91 		if (virtio_id_match(dev, &ids[i]))
92 			return 1;
93 	return 0;
94 }
95 
96 static int virtio_uevent(struct device *_dv, struct kobj_uevent_env *env)
97 {
98 	struct virtio_device *dev = dev_to_virtio(_dv);
99 
100 	return add_uevent_var(env, "MODALIAS=virtio:d%08Xv%08X",
101 			      dev->id.device, dev->id.vendor);
102 }
103 
104 void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
105 					 unsigned int fbit)
106 {
107 	unsigned int i;
108 	struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver);
109 
110 	for (i = 0; i < drv->feature_table_size; i++)
111 		if (drv->feature_table[i] == fbit)
112 			return;
113 
114 	if (drv->feature_table_legacy) {
115 		for (i = 0; i < drv->feature_table_size_legacy; i++)
116 			if (drv->feature_table_legacy[i] == fbit)
117 				return;
118 	}
119 
120 	BUG();
121 }
122 EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);
123 
124 static void __virtio_config_changed(struct virtio_device *dev)
125 {
126 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
127 
128 	if (!dev->config_enabled)
129 		dev->config_change_pending = true;
130 	else if (drv && drv->config_changed)
131 		drv->config_changed(dev);
132 }
133 
134 void virtio_config_changed(struct virtio_device *dev)
135 {
136 	unsigned long flags;
137 
138 	spin_lock_irqsave(&dev->config_lock, flags);
139 	__virtio_config_changed(dev);
140 	spin_unlock_irqrestore(&dev->config_lock, flags);
141 }
142 EXPORT_SYMBOL_GPL(virtio_config_changed);
143 
144 static void virtio_config_disable(struct virtio_device *dev)
145 {
146 	spin_lock_irq(&dev->config_lock);
147 	dev->config_enabled = false;
148 	spin_unlock_irq(&dev->config_lock);
149 }
150 
151 static void virtio_config_enable(struct virtio_device *dev)
152 {
153 	spin_lock_irq(&dev->config_lock);
154 	dev->config_enabled = true;
155 	if (dev->config_change_pending)
156 		__virtio_config_changed(dev);
157 	dev->config_change_pending = false;
158 	spin_unlock_irq(&dev->config_lock);
159 }
160 
161 void virtio_add_status(struct virtio_device *dev, unsigned int status)
162 {
163 	might_sleep();
164 	dev->config->set_status(dev, dev->config->get_status(dev) | status);
165 }
166 EXPORT_SYMBOL_GPL(virtio_add_status);
167 
168 int virtio_finalize_features(struct virtio_device *dev)
169 {
170 	int ret = dev->config->finalize_features(dev);
171 	unsigned status;
172 
173 	might_sleep();
174 	if (ret)
175 		return ret;
176 
177 	ret = arch_has_restricted_virtio_memory_access();
178 	if (ret) {
179 		if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
180 			dev_warn(&dev->dev,
181 				 "device must provide VIRTIO_F_VERSION_1\n");
182 			return -ENODEV;
183 		}
184 
185 		if (!virtio_has_feature(dev, VIRTIO_F_ACCESS_PLATFORM)) {
186 			dev_warn(&dev->dev,
187 				 "device must provide VIRTIO_F_ACCESS_PLATFORM\n");
188 			return -ENODEV;
189 		}
190 	}
191 
192 	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
193 		return 0;
194 
195 	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
196 	status = dev->config->get_status(dev);
197 	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
198 		dev_err(&dev->dev, "virtio: device refuses features: %x\n",
199 			status);
200 		return -ENODEV;
201 	}
202 	return 0;
203 }
204 EXPORT_SYMBOL_GPL(virtio_finalize_features);
205 
206 static int virtio_dev_probe(struct device *_d)
207 {
208 	int err, i;
209 	struct virtio_device *dev = dev_to_virtio(_d);
210 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
211 	u64 device_features;
212 	u64 driver_features;
213 	u64 driver_features_legacy;
214 
215 	/* We have a driver! */
216 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
217 
218 	/* Figure out what features the device supports. */
219 	device_features = dev->config->get_features(dev);
220 
221 	/* Figure out what features the driver supports. */
222 	driver_features = 0;
223 	for (i = 0; i < drv->feature_table_size; i++) {
224 		unsigned int f = drv->feature_table[i];
225 		BUG_ON(f >= 64);
226 		driver_features |= (1ULL << f);
227 	}
228 
229 	/* Some drivers have a separate feature table for virtio v1.0 */
230 	if (drv->feature_table_legacy) {
231 		driver_features_legacy = 0;
232 		for (i = 0; i < drv->feature_table_size_legacy; i++) {
233 			unsigned int f = drv->feature_table_legacy[i];
234 			BUG_ON(f >= 64);
235 			driver_features_legacy |= (1ULL << f);
236 		}
237 	} else {
238 		driver_features_legacy = driver_features;
239 	}
240 
241 	if (device_features & (1ULL << VIRTIO_F_VERSION_1))
242 		dev->features = driver_features & device_features;
243 	else
244 		dev->features = driver_features_legacy & device_features;
245 
246 	/* Transport features always preserved to pass to finalize_features. */
247 	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)
248 		if (device_features & (1ULL << i))
249 			__virtio_set_bit(dev, i);
250 
251 	if (drv->validate) {
252 		err = drv->validate(dev);
253 		if (err)
254 			goto err;
255 	}
256 
257 	err = virtio_finalize_features(dev);
258 	if (err)
259 		goto err;
260 
261 	err = drv->probe(dev);
262 	if (err)
263 		goto err;
264 
265 	/* If probe didn't do it, mark device DRIVER_OK ourselves. */
266 	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
267 		virtio_device_ready(dev);
268 
269 	if (drv->scan)
270 		drv->scan(dev);
271 
272 	virtio_config_enable(dev);
273 
274 	return 0;
275 err:
276 	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
277 	return err;
278 
279 }
280 
281 static void virtio_dev_remove(struct device *_d)
282 {
283 	struct virtio_device *dev = dev_to_virtio(_d);
284 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
285 
286 	virtio_config_disable(dev);
287 
288 	drv->remove(dev);
289 
290 	/* Driver should have reset device. */
291 	WARN_ON_ONCE(dev->config->get_status(dev));
292 
293 	/* Acknowledge the device's existence again. */
294 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
295 }
296 
297 static struct bus_type virtio_bus = {
298 	.name  = "virtio",
299 	.match = virtio_dev_match,
300 	.dev_groups = virtio_dev_groups,
301 	.uevent = virtio_uevent,
302 	.probe = virtio_dev_probe,
303 	.remove = virtio_dev_remove,
304 };
305 
306 int register_virtio_driver(struct virtio_driver *driver)
307 {
308 	/* Catch this early. */
309 	BUG_ON(driver->feature_table_size && !driver->feature_table);
310 	driver->driver.bus = &virtio_bus;
311 	return driver_register(&driver->driver);
312 }
313 EXPORT_SYMBOL_GPL(register_virtio_driver);
314 
315 void unregister_virtio_driver(struct virtio_driver *driver)
316 {
317 	driver_unregister(&driver->driver);
318 }
319 EXPORT_SYMBOL_GPL(unregister_virtio_driver);
320 
321 /**
322  * register_virtio_device - register virtio device
323  * @dev        : virtio device to be registered
324  *
325  * On error, the caller must call put_device on &@dev->dev (and not kfree),
326  * as another code path may have obtained a reference to @dev.
327  *
328  * Returns: 0 on suceess, -error on failure
329  */
330 int register_virtio_device(struct virtio_device *dev)
331 {
332 	int err;
333 
334 	dev->dev.bus = &virtio_bus;
335 	device_initialize(&dev->dev);
336 
337 	/* Assign a unique device index and hence name. */
338 	err = ida_simple_get(&virtio_index_ida, 0, 0, GFP_KERNEL);
339 	if (err < 0)
340 		goto out;
341 
342 	dev->index = err;
343 	dev_set_name(&dev->dev, "virtio%u", dev->index);
344 
345 	spin_lock_init(&dev->config_lock);
346 	dev->config_enabled = false;
347 	dev->config_change_pending = false;
348 
349 	/* We always start by resetting the device, in case a previous
350 	 * driver messed it up.  This also tests that code path a little. */
351 	dev->config->reset(dev);
352 
353 	/* Acknowledge that we've seen the device. */
354 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
355 
356 	INIT_LIST_HEAD(&dev->vqs);
357 
358 	/*
359 	 * device_add() causes the bus infrastructure to look for a matching
360 	 * driver.
361 	 */
362 	err = device_add(&dev->dev);
363 	if (err)
364 		ida_simple_remove(&virtio_index_ida, dev->index);
365 out:
366 	if (err)
367 		virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
368 	return err;
369 }
370 EXPORT_SYMBOL_GPL(register_virtio_device);
371 
372 bool is_virtio_device(struct device *dev)
373 {
374 	return dev->bus == &virtio_bus;
375 }
376 EXPORT_SYMBOL_GPL(is_virtio_device);
377 
378 void unregister_virtio_device(struct virtio_device *dev)
379 {
380 	int index = dev->index; /* save for after device release */
381 
382 	device_unregister(&dev->dev);
383 	ida_simple_remove(&virtio_index_ida, index);
384 }
385 EXPORT_SYMBOL_GPL(unregister_virtio_device);
386 
387 #ifdef CONFIG_PM_SLEEP
388 int virtio_device_freeze(struct virtio_device *dev)
389 {
390 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
391 
392 	virtio_config_disable(dev);
393 
394 	dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
395 
396 	if (drv && drv->freeze)
397 		return drv->freeze(dev);
398 
399 	return 0;
400 }
401 EXPORT_SYMBOL_GPL(virtio_device_freeze);
402 
403 int virtio_device_restore(struct virtio_device *dev)
404 {
405 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
406 	int ret;
407 
408 	/* We always start by resetting the device, in case a previous
409 	 * driver messed it up. */
410 	dev->config->reset(dev);
411 
412 	/* Acknowledge that we've seen the device. */
413 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
414 
415 	/* Maybe driver failed before freeze.
416 	 * Restore the failed status, for debugging. */
417 	if (dev->failed)
418 		virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
419 
420 	if (!drv)
421 		return 0;
422 
423 	/* We have a driver! */
424 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
425 
426 	ret = virtio_finalize_features(dev);
427 	if (ret)
428 		goto err;
429 
430 	if (drv->restore) {
431 		ret = drv->restore(dev);
432 		if (ret)
433 			goto err;
434 	}
435 
436 	/* Finally, tell the device we're all set */
437 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
438 
439 	virtio_config_enable(dev);
440 
441 	return 0;
442 
443 err:
444 	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
445 	return ret;
446 }
447 EXPORT_SYMBOL_GPL(virtio_device_restore);
448 #endif
449 
450 static int virtio_init(void)
451 {
452 	if (bus_register(&virtio_bus) != 0)
453 		panic("virtio bus registration failed");
454 	return 0;
455 }
456 
457 static void __exit virtio_exit(void)
458 {
459 	bus_unregister(&virtio_bus);
460 	ida_destroy(&virtio_index_ida);
461 }
462 core_initcall(virtio_init);
463 module_exit(virtio_exit);
464 
465 MODULE_LICENSE("GPL");
466