xref: /openbmc/linux/drivers/virtio/virtio_mmio.c (revision c819e2cf)
1 /*
2  * Virtio memory mapped device driver
3  *
4  * Copyright 2011, ARM Ltd.
5  *
6  * This module allows virtio devices to be used over a virtual, memory mapped
7  * platform device.
8  *
9  * The guest device(s) may be instantiated in one of three equivalent ways:
10  *
11  * 1. Static platform device in board's code, eg.:
12  *
13  *	static struct platform_device v2m_virtio_device = {
14  *		.name = "virtio-mmio",
15  *		.id = -1,
16  *		.num_resources = 2,
17  *		.resource = (struct resource []) {
18  *			{
19  *				.start = 0x1001e000,
20  *				.end = 0x1001e0ff,
21  *				.flags = IORESOURCE_MEM,
22  *			}, {
23  *				.start = 42 + 32,
24  *				.end = 42 + 32,
25  *				.flags = IORESOURCE_IRQ,
26  *			},
27  *		}
28  *	};
29  *
30  * 2. Device Tree node, eg.:
31  *
32  *		virtio_block@1e000 {
33  *			compatible = "virtio,mmio";
34  *			reg = <0x1e000 0x100>;
35  *			interrupts = <42>;
36  *		}
37  *
38  * 3. Kernel module (or command line) parameter. Can be used more than once -
39  *    one device will be created for each one. Syntax:
40  *
41  *		[virtio_mmio.]device=<size>@<baseaddr>:<irq>[:<id>]
42  *    where:
43  *		<size>     := size (can use standard suffixes like K, M or G)
44  *		<baseaddr> := physical base address
45  *		<irq>      := interrupt number (as passed to request_irq())
46  *		<id>       := (optional) platform device id
47  *    eg.:
48  *		virtio_mmio.device=0x100@0x100b0000:48 \
49  *				virtio_mmio.device=1K@0x1001e000:74
50  *
51  *
52  *
53  * Registers layout (all 32-bit wide):
54  *
55  * offset d. name             description
56  * ------ -- ---------------- -----------------
57  *
58  * 0x000  R  MagicValue       Magic value "virt"
59  * 0x004  R  Version          Device version (current max. 1)
60  * 0x008  R  DeviceID         Virtio device ID
61  * 0x00c  R  VendorID         Virtio vendor ID
62  *
63  * 0x010  R  HostFeatures     Features supported by the host
64  * 0x014  W  HostFeaturesSel  Set of host features to access via HostFeatures
65  *
66  * 0x020  W  GuestFeatures    Features activated by the guest
67  * 0x024  W  GuestFeaturesSel Set of activated features to set via GuestFeatures
68  * 0x028  W  GuestPageSize    Size of guest's memory page in bytes
69  *
70  * 0x030  W  QueueSel         Queue selector
71  * 0x034  R  QueueNumMax      Maximum size of the currently selected queue
72  * 0x038  W  QueueNum         Queue size for the currently selected queue
73  * 0x03c  W  QueueAlign       Used Ring alignment for the current queue
74  * 0x040  RW QueuePFN         PFN for the currently selected queue
75  *
76  * 0x050  W  QueueNotify      Queue notifier
77  * 0x060  R  InterruptStatus  Interrupt status register
78  * 0x064  W  InterruptACK     Interrupt acknowledge register
79  * 0x070  RW Status           Device status register
80  *
81  * 0x100+ RW                  Device-specific configuration space
82  *
83  * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
84  *
85  * This work is licensed under the terms of the GNU GPL, version 2 or later.
86  * See the COPYING file in the top-level directory.
87  */
88 
89 #define pr_fmt(fmt) "virtio-mmio: " fmt
90 
91 #include <linux/highmem.h>
92 #include <linux/interrupt.h>
93 #include <linux/io.h>
94 #include <linux/list.h>
95 #include <linux/module.h>
96 #include <linux/platform_device.h>
97 #include <linux/slab.h>
98 #include <linux/spinlock.h>
99 #include <linux/virtio.h>
100 #include <linux/virtio_config.h>
101 #include <linux/virtio_mmio.h>
102 #include <linux/virtio_ring.h>
103 
104 
105 
106 /* The alignment to use between consumer and producer parts of vring.
107  * Currently hardcoded to the page size. */
108 #define VIRTIO_MMIO_VRING_ALIGN		PAGE_SIZE
109 
110 
111 
112 #define to_virtio_mmio_device(_plat_dev) \
113 	container_of(_plat_dev, struct virtio_mmio_device, vdev)
114 
115 struct virtio_mmio_device {
116 	struct virtio_device vdev;
117 	struct platform_device *pdev;
118 
119 	void __iomem *base;
120 	unsigned long version;
121 
122 	/* a list of queues so we can dispatch IRQs */
123 	spinlock_t lock;
124 	struct list_head virtqueues;
125 };
126 
127 struct virtio_mmio_vq_info {
128 	/* the actual virtqueue */
129 	struct virtqueue *vq;
130 
131 	/* the number of entries in the queue */
132 	unsigned int num;
133 
134 	/* the virtual address of the ring queue */
135 	void *queue;
136 
137 	/* the list node for the virtqueues list */
138 	struct list_head node;
139 };
140 
141 
142 
143 /* Configuration interface */
144 
145 static u64 vm_get_features(struct virtio_device *vdev)
146 {
147 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
148 
149 	/* TODO: Features > 32 bits */
150 	writel(0, vm_dev->base + VIRTIO_MMIO_HOST_FEATURES_SEL);
151 
152 	return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
153 }
154 
155 static int vm_finalize_features(struct virtio_device *vdev)
156 {
157 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
158 
159 	/* Give virtio_ring a chance to accept features. */
160 	vring_transport_features(vdev);
161 
162 	/* Make sure we don't have any features > 32 bits! */
163 	BUG_ON((u32)vdev->features != vdev->features);
164 
165 	writel(0, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
166 	writel(vdev->features, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
167 
168 	return 0;
169 }
170 
171 static void vm_get(struct virtio_device *vdev, unsigned offset,
172 		   void *buf, unsigned len)
173 {
174 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
175 	u8 *ptr = buf;
176 	int i;
177 
178 	for (i = 0; i < len; i++)
179 		ptr[i] = readb(vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
180 }
181 
182 static void vm_set(struct virtio_device *vdev, unsigned offset,
183 		   const void *buf, unsigned len)
184 {
185 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
186 	const u8 *ptr = buf;
187 	int i;
188 
189 	for (i = 0; i < len; i++)
190 		writeb(ptr[i], vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
191 }
192 
193 static u8 vm_get_status(struct virtio_device *vdev)
194 {
195 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
196 
197 	return readl(vm_dev->base + VIRTIO_MMIO_STATUS) & 0xff;
198 }
199 
200 static void vm_set_status(struct virtio_device *vdev, u8 status)
201 {
202 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
203 
204 	/* We should never be setting status to 0. */
205 	BUG_ON(status == 0);
206 
207 	writel(status, vm_dev->base + VIRTIO_MMIO_STATUS);
208 }
209 
210 static void vm_reset(struct virtio_device *vdev)
211 {
212 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
213 
214 	/* 0 status means a reset. */
215 	writel(0, vm_dev->base + VIRTIO_MMIO_STATUS);
216 }
217 
218 
219 
220 /* Transport interface */
221 
222 /* the notify function used when creating a virt queue */
223 static bool vm_notify(struct virtqueue *vq)
224 {
225 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
226 
227 	/* We write the queue's selector into the notification register to
228 	 * signal the other end */
229 	writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
230 	return true;
231 }
232 
233 /* Notify all virtqueues on an interrupt. */
234 static irqreturn_t vm_interrupt(int irq, void *opaque)
235 {
236 	struct virtio_mmio_device *vm_dev = opaque;
237 	struct virtio_mmio_vq_info *info;
238 	unsigned long status;
239 	unsigned long flags;
240 	irqreturn_t ret = IRQ_NONE;
241 
242 	/* Read and acknowledge interrupts */
243 	status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS);
244 	writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK);
245 
246 	if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)) {
247 		virtio_config_changed(&vm_dev->vdev);
248 		ret = IRQ_HANDLED;
249 	}
250 
251 	if (likely(status & VIRTIO_MMIO_INT_VRING)) {
252 		spin_lock_irqsave(&vm_dev->lock, flags);
253 		list_for_each_entry(info, &vm_dev->virtqueues, node)
254 			ret |= vring_interrupt(irq, info->vq);
255 		spin_unlock_irqrestore(&vm_dev->lock, flags);
256 	}
257 
258 	return ret;
259 }
260 
261 
262 
263 static void vm_del_vq(struct virtqueue *vq)
264 {
265 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
266 	struct virtio_mmio_vq_info *info = vq->priv;
267 	unsigned long flags, size;
268 	unsigned int index = vq->index;
269 
270 	spin_lock_irqsave(&vm_dev->lock, flags);
271 	list_del(&info->node);
272 	spin_unlock_irqrestore(&vm_dev->lock, flags);
273 
274 	vring_del_virtqueue(vq);
275 
276 	/* Select and deactivate the queue */
277 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
278 	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
279 
280 	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_MMIO_VRING_ALIGN));
281 	free_pages_exact(info->queue, size);
282 	kfree(info);
283 }
284 
285 static void vm_del_vqs(struct virtio_device *vdev)
286 {
287 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
288 	struct virtqueue *vq, *n;
289 
290 	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
291 		vm_del_vq(vq);
292 
293 	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
294 }
295 
296 
297 
298 static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
299 				  void (*callback)(struct virtqueue *vq),
300 				  const char *name)
301 {
302 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
303 	struct virtio_mmio_vq_info *info;
304 	struct virtqueue *vq;
305 	unsigned long flags, size;
306 	int err;
307 
308 	if (!name)
309 		return NULL;
310 
311 	/* Select the queue we're interested in */
312 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
313 
314 	/* Queue shouldn't already be set up. */
315 	if (readl(vm_dev->base + VIRTIO_MMIO_QUEUE_PFN)) {
316 		err = -ENOENT;
317 		goto error_available;
318 	}
319 
320 	/* Allocate and fill out our active queue description */
321 	info = kmalloc(sizeof(*info), GFP_KERNEL);
322 	if (!info) {
323 		err = -ENOMEM;
324 		goto error_kmalloc;
325 	}
326 
327 	/* Allocate pages for the queue - start with a queue as big as
328 	 * possible (limited by maximum size allowed by device), drop down
329 	 * to a minimal size, just big enough to fit descriptor table
330 	 * and two rings (which makes it "alignment_size * 2")
331 	 */
332 	info->num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
333 
334 	/* If the device reports a 0 entry queue, we won't be able to
335 	 * use it to perform I/O, and vring_new_virtqueue() can't create
336 	 * empty queues anyway, so don't bother to set up the device.
337 	 */
338 	if (info->num == 0) {
339 		err = -ENOENT;
340 		goto error_alloc_pages;
341 	}
342 
343 	while (1) {
344 		size = PAGE_ALIGN(vring_size(info->num,
345 				VIRTIO_MMIO_VRING_ALIGN));
346 		/* Did the last iter shrink the queue below minimum size? */
347 		if (size < VIRTIO_MMIO_VRING_ALIGN * 2) {
348 			err = -ENOMEM;
349 			goto error_alloc_pages;
350 		}
351 
352 		info->queue = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO);
353 		if (info->queue)
354 			break;
355 
356 		info->num /= 2;
357 	}
358 
359 	/* Activate the queue */
360 	writel(info->num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
361 	writel(VIRTIO_MMIO_VRING_ALIGN,
362 			vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
363 	writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
364 			vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
365 
366 	/* Create the vring */
367 	vq = vring_new_virtqueue(index, info->num, VIRTIO_MMIO_VRING_ALIGN, vdev,
368 				 true, info->queue, vm_notify, callback, name);
369 	if (!vq) {
370 		err = -ENOMEM;
371 		goto error_new_virtqueue;
372 	}
373 
374 	vq->priv = info;
375 	info->vq = vq;
376 
377 	spin_lock_irqsave(&vm_dev->lock, flags);
378 	list_add(&info->node, &vm_dev->virtqueues);
379 	spin_unlock_irqrestore(&vm_dev->lock, flags);
380 
381 	return vq;
382 
383 error_new_virtqueue:
384 	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
385 	free_pages_exact(info->queue, size);
386 error_alloc_pages:
387 	kfree(info);
388 error_kmalloc:
389 error_available:
390 	return ERR_PTR(err);
391 }
392 
393 static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
394 		       struct virtqueue *vqs[],
395 		       vq_callback_t *callbacks[],
396 		       const char *names[])
397 {
398 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
399 	unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
400 	int i, err;
401 
402 	err = request_irq(irq, vm_interrupt, IRQF_SHARED,
403 			dev_name(&vdev->dev), vm_dev);
404 	if (err)
405 		return err;
406 
407 	for (i = 0; i < nvqs; ++i) {
408 		vqs[i] = vm_setup_vq(vdev, i, callbacks[i], names[i]);
409 		if (IS_ERR(vqs[i])) {
410 			vm_del_vqs(vdev);
411 			return PTR_ERR(vqs[i]);
412 		}
413 	}
414 
415 	return 0;
416 }
417 
418 static const char *vm_bus_name(struct virtio_device *vdev)
419 {
420 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
421 
422 	return vm_dev->pdev->name;
423 }
424 
425 static const struct virtio_config_ops virtio_mmio_config_ops = {
426 	.get		= vm_get,
427 	.set		= vm_set,
428 	.get_status	= vm_get_status,
429 	.set_status	= vm_set_status,
430 	.reset		= vm_reset,
431 	.find_vqs	= vm_find_vqs,
432 	.del_vqs	= vm_del_vqs,
433 	.get_features	= vm_get_features,
434 	.finalize_features = vm_finalize_features,
435 	.bus_name	= vm_bus_name,
436 };
437 
438 
439 
440 /* Platform device */
441 
442 static int virtio_mmio_probe(struct platform_device *pdev)
443 {
444 	struct virtio_mmio_device *vm_dev;
445 	struct resource *mem;
446 	unsigned long magic;
447 
448 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
449 	if (!mem)
450 		return -EINVAL;
451 
452 	if (!devm_request_mem_region(&pdev->dev, mem->start,
453 			resource_size(mem), pdev->name))
454 		return -EBUSY;
455 
456 	vm_dev = devm_kzalloc(&pdev->dev, sizeof(*vm_dev), GFP_KERNEL);
457 	if (!vm_dev)
458 		return  -ENOMEM;
459 
460 	vm_dev->vdev.dev.parent = &pdev->dev;
461 	vm_dev->vdev.config = &virtio_mmio_config_ops;
462 	vm_dev->pdev = pdev;
463 	INIT_LIST_HEAD(&vm_dev->virtqueues);
464 	spin_lock_init(&vm_dev->lock);
465 
466 	vm_dev->base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
467 	if (vm_dev->base == NULL)
468 		return -EFAULT;
469 
470 	/* Check magic value */
471 	magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);
472 	if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {
473 		dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!\n", magic);
474 		return -ENODEV;
475 	}
476 
477 	/* Check device version */
478 	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
479 	if (vm_dev->version != 1) {
480 		dev_err(&pdev->dev, "Version %ld not supported!\n",
481 				vm_dev->version);
482 		return -ENXIO;
483 	}
484 
485 	vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
486 	vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
487 
488 	writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
489 
490 	platform_set_drvdata(pdev, vm_dev);
491 
492 	return register_virtio_device(&vm_dev->vdev);
493 }
494 
495 static int virtio_mmio_remove(struct platform_device *pdev)
496 {
497 	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
498 
499 	unregister_virtio_device(&vm_dev->vdev);
500 
501 	return 0;
502 }
503 
504 
505 
506 /* Devices list parameter */
507 
508 #if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)
509 
510 static struct device vm_cmdline_parent = {
511 	.init_name = "virtio-mmio-cmdline",
512 };
513 
514 static int vm_cmdline_parent_registered;
515 static int vm_cmdline_id;
516 
517 static int vm_cmdline_set(const char *device,
518 		const struct kernel_param *kp)
519 {
520 	int err;
521 	struct resource resources[2] = {};
522 	char *str;
523 	long long int base, size;
524 	unsigned int irq;
525 	int processed, consumed = 0;
526 	struct platform_device *pdev;
527 
528 	/* Consume "size" part of the command line parameter */
529 	size = memparse(device, &str);
530 
531 	/* Get "@<base>:<irq>[:<id>]" chunks */
532 	processed = sscanf(str, "@%lli:%u%n:%d%n",
533 			&base, &irq, &consumed,
534 			&vm_cmdline_id, &consumed);
535 
536 	/*
537 	 * sscanf() must processes at least 2 chunks; also there
538 	 * must be no extra characters after the last chunk, so
539 	 * str[consumed] must be '\0'
540 	 */
541 	if (processed < 2 || str[consumed])
542 		return -EINVAL;
543 
544 	resources[0].flags = IORESOURCE_MEM;
545 	resources[0].start = base;
546 	resources[0].end = base + size - 1;
547 
548 	resources[1].flags = IORESOURCE_IRQ;
549 	resources[1].start = resources[1].end = irq;
550 
551 	if (!vm_cmdline_parent_registered) {
552 		err = device_register(&vm_cmdline_parent);
553 		if (err) {
554 			pr_err("Failed to register parent device!\n");
555 			return err;
556 		}
557 		vm_cmdline_parent_registered = 1;
558 	}
559 
560 	pr_info("Registering device virtio-mmio.%d at 0x%llx-0x%llx, IRQ %d.\n",
561 		       vm_cmdline_id,
562 		       (unsigned long long)resources[0].start,
563 		       (unsigned long long)resources[0].end,
564 		       (int)resources[1].start);
565 
566 	pdev = platform_device_register_resndata(&vm_cmdline_parent,
567 			"virtio-mmio", vm_cmdline_id++,
568 			resources, ARRAY_SIZE(resources), NULL, 0);
569 	if (IS_ERR(pdev))
570 		return PTR_ERR(pdev);
571 
572 	return 0;
573 }
574 
575 static int vm_cmdline_get_device(struct device *dev, void *data)
576 {
577 	char *buffer = data;
578 	unsigned int len = strlen(buffer);
579 	struct platform_device *pdev = to_platform_device(dev);
580 
581 	snprintf(buffer + len, PAGE_SIZE - len, "0x%llx@0x%llx:%llu:%d\n",
582 			pdev->resource[0].end - pdev->resource[0].start + 1ULL,
583 			(unsigned long long)pdev->resource[0].start,
584 			(unsigned long long)pdev->resource[1].start,
585 			pdev->id);
586 	return 0;
587 }
588 
589 static int vm_cmdline_get(char *buffer, const struct kernel_param *kp)
590 {
591 	buffer[0] = '\0';
592 	device_for_each_child(&vm_cmdline_parent, buffer,
593 			vm_cmdline_get_device);
594 	return strlen(buffer) + 1;
595 }
596 
597 static struct kernel_param_ops vm_cmdline_param_ops = {
598 	.set = vm_cmdline_set,
599 	.get = vm_cmdline_get,
600 };
601 
602 device_param_cb(device, &vm_cmdline_param_ops, NULL, S_IRUSR);
603 
604 static int vm_unregister_cmdline_device(struct device *dev,
605 		void *data)
606 {
607 	platform_device_unregister(to_platform_device(dev));
608 
609 	return 0;
610 }
611 
612 static void vm_unregister_cmdline_devices(void)
613 {
614 	if (vm_cmdline_parent_registered) {
615 		device_for_each_child(&vm_cmdline_parent, NULL,
616 				vm_unregister_cmdline_device);
617 		device_unregister(&vm_cmdline_parent);
618 		vm_cmdline_parent_registered = 0;
619 	}
620 }
621 
622 #else
623 
624 static void vm_unregister_cmdline_devices(void)
625 {
626 }
627 
628 #endif
629 
630 /* Platform driver */
631 
632 static struct of_device_id virtio_mmio_match[] = {
633 	{ .compatible = "virtio,mmio", },
634 	{},
635 };
636 MODULE_DEVICE_TABLE(of, virtio_mmio_match);
637 
638 static struct platform_driver virtio_mmio_driver = {
639 	.probe		= virtio_mmio_probe,
640 	.remove		= virtio_mmio_remove,
641 	.driver		= {
642 		.name	= "virtio-mmio",
643 		.of_match_table	= virtio_mmio_match,
644 	},
645 };
646 
647 static int __init virtio_mmio_init(void)
648 {
649 	return platform_driver_register(&virtio_mmio_driver);
650 }
651 
652 static void __exit virtio_mmio_exit(void)
653 {
654 	platform_driver_unregister(&virtio_mmio_driver);
655 	vm_unregister_cmdline_devices();
656 }
657 
658 module_init(virtio_mmio_init);
659 module_exit(virtio_mmio_exit);
660 
661 MODULE_AUTHOR("Pawel Moll <pawel.moll@arm.com>");
662 MODULE_DESCRIPTION("Platform bus driver for memory mapped virtio devices");
663 MODULE_LICENSE("GPL");
664