xref: /linux/include/linux/virtio_config.h (revision 8ca154e4910efff1b04e7750e007d75732c68323)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_VIRTIO_CONFIG_H
3 #define _LINUX_VIRTIO_CONFIG_H
4 
5 #include <linux/err.h>
6 #include <linux/bug.h>
7 #include <linux/virtio.h>
8 #include <linux/virtio_byteorder.h>
9 #include <linux/compiler_types.h>
10 #include <uapi/linux/virtio_config.h>
11 
12 struct irq_affinity;
13 
14 struct virtio_shm_region {
15 	u64 addr;
16 	u64 len;
17 };
18 
19 typedef void vq_callback_t(struct virtqueue *);
20 
21 /**
22  * struct virtqueue_info - Info for a virtqueue passed to find_vqs().
23  * @name: virtqueue description. Used mainly for debugging, NULL for
24  *        a virtqueue unused by the driver.
25  * @callback: A callback to invoke on a used buffer notification.
26  *            NULL for a virtqueue that does not need a callback.
27  * @ctx: A flag to indicate to maintain an extra context per virtqueue.
28  */
29 struct virtqueue_info {
30 	const char *name;
31 	vq_callback_t *callback;
32 	bool ctx;
33 };
34 
35 /**
36  * struct virtio_config_ops - operations for configuring a virtio device
37  * Note: Do not assume that a transport implements all of the operations
38  *       getting/setting a value as a simple read/write! Generally speaking,
39  *       any of @get/@set, @get_status/@set_status, or @get_features/
40  *       @finalize_features are NOT safe to be called from an atomic
41  *       context.
42  * @get: read the value of a configuration field
43  *	vdev: the virtio_device
44  *	offset: the offset of the configuration field
45  *	buf: the buffer to write the field value into.
46  *	len: the length of the buffer
47  * @set: write the value of a configuration field
48  *	vdev: the virtio_device
49  *	offset: the offset of the configuration field
50  *	buf: the buffer to read the field value from.
51  *	len: the length of the buffer
52  * @generation: config generation counter (optional)
53  *	vdev: the virtio_device
54  *	Returns the config generation counter
55  * @get_status: read the status byte
56  *	vdev: the virtio_device
57  *	Returns the status byte
58  * @set_status: write the status byte
59  *	vdev: the virtio_device
60  *	status: the new status byte
61  * @reset: reset the device
62  *	vdev: the virtio device
63  *	After this, status and feature negotiation must be done again
64  *	Device must not be reset from its vq/config callbacks, or in
65  *	parallel with being added/removed.
66  * @find_vqs: find virtqueues and instantiate them.
67  *	vdev: the virtio_device
68  *	nvqs: the number of virtqueues to find
69  *	vqs: on success, includes new virtqueues
70  *	vqs_info: array of virtqueue info structures
71  *	Returns 0 on success or error status
72  * @del_vqs: free virtqueues found by find_vqs().
73  * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
74  *      The function guarantees that all memory operations on the
75  *      queue before it are visible to the vring_interrupt() that is
76  *      called after it.
77  *      vdev: the virtio_device
78  * @get_features: get the array of feature bits for this device.
79  *	vdev: the virtio_device
80  *	Returns the first 64 feature bits (all we currently need).
81  * @finalize_features: confirm what device features we'll be using.
82  *	vdev: the virtio_device
83  *	This sends the driver feature bits to the device: it can change
84  *	the dev->feature bits if it wants.
85  *	Note that despite the name this	can be called any number of
86  *	times.
87  *	Returns 0 on success or error status
88  * @bus_name: return the bus name associated with the device (optional)
89  *	vdev: the virtio_device
90  *      This returns a pointer to the bus name a la pci_name from which
91  *      the caller can then copy.
92  * @set_vq_affinity: set the affinity for a virtqueue (optional).
93  * @get_vq_affinity: get the affinity for a virtqueue (optional).
94  * @get_shm_region: get a shared memory region based on the index.
95  * @disable_vq_and_reset: reset a queue individually (optional).
96  *	vq: the virtqueue
97  *	Returns 0 on success or error status
98  *	disable_vq_and_reset will guarantee that the callbacks are disabled and
99  *	synchronized.
100  *	Except for the callback, the caller should guarantee that the vring is
101  *	not accessed by any functions of virtqueue.
102  * @enable_vq_after_reset: enable a reset queue
103  *	vq: the virtqueue
104  *	Returns 0 on success or error status
105  *	If disable_vq_and_reset is set, then enable_vq_after_reset must also be
106  *	set.
107  */
108 struct virtio_config_ops {
109 	void (*get)(struct virtio_device *vdev, unsigned offset,
110 		    void *buf, unsigned len);
111 	void (*set)(struct virtio_device *vdev, unsigned offset,
112 		    const void *buf, unsigned len);
113 	u32 (*generation)(struct virtio_device *vdev);
114 	u8 (*get_status)(struct virtio_device *vdev);
115 	void (*set_status)(struct virtio_device *vdev, u8 status);
116 	void (*reset)(struct virtio_device *vdev);
117 	int (*find_vqs)(struct virtio_device *vdev, unsigned int nvqs,
118 			struct virtqueue *vqs[],
119 			struct virtqueue_info vqs_info[],
120 			struct irq_affinity *desc);
121 	void (*del_vqs)(struct virtio_device *);
122 	void (*synchronize_cbs)(struct virtio_device *);
123 	u64 (*get_features)(struct virtio_device *vdev);
124 	int (*finalize_features)(struct virtio_device *vdev);
125 	const char *(*bus_name)(struct virtio_device *vdev);
126 	int (*set_vq_affinity)(struct virtqueue *vq,
127 			       const struct cpumask *cpu_mask);
128 	const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,
129 						 int index);
130 	bool (*get_shm_region)(struct virtio_device *vdev,
131 			       struct virtio_shm_region *region, u8 id);
132 	int (*disable_vq_and_reset)(struct virtqueue *vq);
133 	int (*enable_vq_after_reset)(struct virtqueue *vq);
134 };
135 
136 /* If driver didn't advertise the feature, it will never appear. */
137 void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
138 					 unsigned int fbit);
139 
140 /**
141  * __virtio_test_bit - helper to test feature bits. For use by transports.
142  *                     Devices should normally use virtio_has_feature,
143  *                     which includes more checks.
144  * @vdev: the device
145  * @fbit: the feature bit
146  */
__virtio_test_bit(const struct virtio_device * vdev,unsigned int fbit)147 static inline bool __virtio_test_bit(const struct virtio_device *vdev,
148 				     unsigned int fbit)
149 {
150 	/* Did you forget to fix assumptions on max features? */
151 	if (__builtin_constant_p(fbit))
152 		BUILD_BUG_ON(fbit >= 64);
153 	else
154 		BUG_ON(fbit >= 64);
155 
156 	return vdev->features & BIT_ULL(fbit);
157 }
158 
159 /**
160  * __virtio_set_bit - helper to set feature bits. For use by transports.
161  * @vdev: the device
162  * @fbit: the feature bit
163  */
__virtio_set_bit(struct virtio_device * vdev,unsigned int fbit)164 static inline void __virtio_set_bit(struct virtio_device *vdev,
165 				    unsigned int fbit)
166 {
167 	/* Did you forget to fix assumptions on max features? */
168 	if (__builtin_constant_p(fbit))
169 		BUILD_BUG_ON(fbit >= 64);
170 	else
171 		BUG_ON(fbit >= 64);
172 
173 	vdev->features |= BIT_ULL(fbit);
174 }
175 
176 /**
177  * __virtio_clear_bit - helper to clear feature bits. For use by transports.
178  * @vdev: the device
179  * @fbit: the feature bit
180  */
__virtio_clear_bit(struct virtio_device * vdev,unsigned int fbit)181 static inline void __virtio_clear_bit(struct virtio_device *vdev,
182 				      unsigned int fbit)
183 {
184 	/* Did you forget to fix assumptions on max features? */
185 	if (__builtin_constant_p(fbit))
186 		BUILD_BUG_ON(fbit >= 64);
187 	else
188 		BUG_ON(fbit >= 64);
189 
190 	vdev->features &= ~BIT_ULL(fbit);
191 }
192 
193 /**
194  * virtio_has_feature - helper to determine if this device has this feature.
195  * @vdev: the device
196  * @fbit: the feature bit
197  */
virtio_has_feature(const struct virtio_device * vdev,unsigned int fbit)198 static inline bool virtio_has_feature(const struct virtio_device *vdev,
199 				      unsigned int fbit)
200 {
201 	if (fbit < VIRTIO_TRANSPORT_F_START)
202 		virtio_check_driver_offered_feature(vdev, fbit);
203 
204 	return __virtio_test_bit(vdev, fbit);
205 }
206 
207 /**
208  * virtio_has_dma_quirk - determine whether this device has the DMA quirk
209  * @vdev: the device
210  */
virtio_has_dma_quirk(const struct virtio_device * vdev)211 static inline bool virtio_has_dma_quirk(const struct virtio_device *vdev)
212 {
213 	/*
214 	 * Note the reverse polarity of the quirk feature (compared to most
215 	 * other features), this is for compatibility with legacy systems.
216 	 */
217 	return !virtio_has_feature(vdev, VIRTIO_F_ACCESS_PLATFORM);
218 }
219 
220 static inline
virtio_find_vqs(struct virtio_device * vdev,unsigned int nvqs,struct virtqueue * vqs[],struct virtqueue_info vqs_info[],struct irq_affinity * desc)221 int virtio_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
222 		    struct virtqueue *vqs[],
223 		    struct virtqueue_info vqs_info[],
224 		    struct irq_affinity *desc)
225 {
226 	return vdev->config->find_vqs(vdev, nvqs, vqs, vqs_info, desc);
227 }
228 
229 static inline
virtio_find_single_vq(struct virtio_device * vdev,vq_callback_t * c,const char * n)230 struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
231 					vq_callback_t *c, const char *n)
232 {
233 	struct virtqueue_info vqs_info[] = {
234 		{ n, c },
235 	};
236 	struct virtqueue *vq;
237 	int err = virtio_find_vqs(vdev, 1, &vq, vqs_info, NULL);
238 
239 	if (err < 0)
240 		return ERR_PTR(err);
241 	return vq;
242 }
243 
244 /**
245  * virtio_synchronize_cbs - synchronize with virtqueue callbacks
246  * @dev: the virtio device
247  */
248 static inline
virtio_synchronize_cbs(struct virtio_device * dev)249 void virtio_synchronize_cbs(struct virtio_device *dev)
250 {
251 	if (dev->config->synchronize_cbs) {
252 		dev->config->synchronize_cbs(dev);
253 	} else {
254 		/*
255 		 * A best effort fallback to synchronize with
256 		 * interrupts, preemption and softirq disabled
257 		 * regions. See comment above synchronize_rcu().
258 		 */
259 		synchronize_rcu();
260 	}
261 }
262 
263 /**
264  * virtio_device_ready - enable vq use in probe function
265  * @dev: the virtio device
266  *
267  * Driver must call this to use vqs in the probe function.
268  *
269  * Note: vqs are enabled automatically after probe returns.
270  */
271 static inline
virtio_device_ready(struct virtio_device * dev)272 void virtio_device_ready(struct virtio_device *dev)
273 {
274 	unsigned status = dev->config->get_status(dev);
275 
276 	WARN_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
277 
278 #ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
279 	/*
280 	 * The virtio_synchronize_cbs() makes sure vring_interrupt()
281 	 * will see the driver specific setup if it sees vq->broken
282 	 * as false (even if the notifications come before DRIVER_OK).
283 	 */
284 	virtio_synchronize_cbs(dev);
285 	__virtio_unbreak_device(dev);
286 #endif
287 	/*
288 	 * The transport should ensure the visibility of vq->broken
289 	 * before setting DRIVER_OK. See the comments for the transport
290 	 * specific set_status() method.
291 	 *
292 	 * A well behaved device will only notify a virtqueue after
293 	 * DRIVER_OK, this means the device should "see" the coherenct
294 	 * memory write that set vq->broken as false which is done by
295 	 * the driver when it sees DRIVER_OK, then the following
296 	 * driver's vring_interrupt() will see vq->broken as false so
297 	 * we won't lose any notification.
298 	 */
299 	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
300 }
301 
302 static inline
virtio_bus_name(struct virtio_device * vdev)303 const char *virtio_bus_name(struct virtio_device *vdev)
304 {
305 	if (!vdev->config->bus_name)
306 		return "virtio";
307 	return vdev->config->bus_name(vdev);
308 }
309 
310 /**
311  * virtqueue_set_affinity - setting affinity for a virtqueue
312  * @vq: the virtqueue
313  * @cpu_mask: the cpu mask
314  *
315  * Pay attention the function are best-effort: the affinity hint may not be set
316  * due to config support, irq type and sharing.
317  *
318  */
319 static inline
virtqueue_set_affinity(struct virtqueue * vq,const struct cpumask * cpu_mask)320 int virtqueue_set_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask)
321 {
322 	struct virtio_device *vdev = vq->vdev;
323 	if (vdev->config->set_vq_affinity)
324 		return vdev->config->set_vq_affinity(vq, cpu_mask);
325 	return 0;
326 }
327 
328 static inline
virtio_get_shm_region(struct virtio_device * vdev,struct virtio_shm_region * region,u8 id)329 bool virtio_get_shm_region(struct virtio_device *vdev,
330 			   struct virtio_shm_region *region, u8 id)
331 {
332 	if (!region->len)
333 		return false;
334 	if (!vdev->config->get_shm_region)
335 		return false;
336 	return vdev->config->get_shm_region(vdev, region, id);
337 }
338 
virtio_is_little_endian(struct virtio_device * vdev)339 static inline bool virtio_is_little_endian(struct virtio_device *vdev)
340 {
341 	return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
342 		virtio_legacy_is_little_endian();
343 }
344 
345 /* Memory accessors */
virtio16_to_cpu(struct virtio_device * vdev,__virtio16 val)346 static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
347 {
348 	return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
349 }
350 
cpu_to_virtio16(struct virtio_device * vdev,u16 val)351 static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
352 {
353 	return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
354 }
355 
virtio32_to_cpu(struct virtio_device * vdev,__virtio32 val)356 static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
357 {
358 	return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
359 }
360 
cpu_to_virtio32(struct virtio_device * vdev,u32 val)361 static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
362 {
363 	return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
364 }
365 
virtio64_to_cpu(struct virtio_device * vdev,__virtio64 val)366 static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
367 {
368 	return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
369 }
370 
cpu_to_virtio64(struct virtio_device * vdev,u64 val)371 static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
372 {
373 	return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
374 }
375 
376 #define virtio_to_cpu(vdev, x) \
377 	_Generic((x), \
378 		__u8: (x), \
379 		__virtio16: virtio16_to_cpu((vdev), (x)), \
380 		__virtio32: virtio32_to_cpu((vdev), (x)), \
381 		__virtio64: virtio64_to_cpu((vdev), (x)) \
382 		)
383 
384 #define cpu_to_virtio(vdev, x, m) \
385 	_Generic((m), \
386 		__u8: (x), \
387 		__virtio16: cpu_to_virtio16((vdev), (x)), \
388 		__virtio32: cpu_to_virtio32((vdev), (x)), \
389 		__virtio64: cpu_to_virtio64((vdev), (x)) \
390 		)
391 
392 #define __virtio_native_type(structname, member) \
393 	typeof(virtio_to_cpu(NULL, ((structname*)0)->member))
394 
395 /* Config space accessors. */
396 #define virtio_cread(vdev, structname, member, ptr)			\
397 	do {								\
398 		typeof(((structname*)0)->member) virtio_cread_v;	\
399 									\
400 		might_sleep();						\
401 		/* Sanity check: must match the member's type */	\
402 		typecheck(typeof(virtio_to_cpu((vdev), virtio_cread_v)), *(ptr)); \
403 									\
404 		switch (sizeof(virtio_cread_v)) {			\
405 		case 1:							\
406 		case 2:							\
407 		case 4:							\
408 			vdev->config->get((vdev), 			\
409 					  offsetof(structname, member), \
410 					  &virtio_cread_v,		\
411 					  sizeof(virtio_cread_v));	\
412 			break;						\
413 		default:						\
414 			__virtio_cread_many((vdev), 			\
415 					  offsetof(structname, member), \
416 					  &virtio_cread_v,		\
417 					  1,				\
418 					  sizeof(virtio_cread_v));	\
419 			break;						\
420 		}							\
421 		*(ptr) = virtio_to_cpu(vdev, virtio_cread_v);		\
422 	} while(0)
423 
424 /* Config space accessors. */
425 #define virtio_cwrite(vdev, structname, member, ptr)			\
426 	do {								\
427 		typeof(((structname*)0)->member) virtio_cwrite_v =	\
428 			cpu_to_virtio(vdev, *(ptr), ((structname*)0)->member); \
429 									\
430 		might_sleep();						\
431 		/* Sanity check: must match the member's type */	\
432 		typecheck(typeof(virtio_to_cpu((vdev), virtio_cwrite_v)), *(ptr)); \
433 									\
434 		vdev->config->set((vdev), offsetof(structname, member),	\
435 				  &virtio_cwrite_v,			\
436 				  sizeof(virtio_cwrite_v));		\
437 	} while(0)
438 
439 /*
440  * Nothing virtio-specific about these, but let's worry about generalizing
441  * these later.
442  */
443 #define virtio_le_to_cpu(x) \
444 	_Generic((x), \
445 		__u8: (u8)(x), \
446 		 __le16: (u16)le16_to_cpu(x), \
447 		 __le32: (u32)le32_to_cpu(x), \
448 		 __le64: (u64)le64_to_cpu(x) \
449 		)
450 
451 #define virtio_cpu_to_le(x, m) \
452 	_Generic((m), \
453 		 __u8: (x), \
454 		 __le16: cpu_to_le16(x), \
455 		 __le32: cpu_to_le32(x), \
456 		 __le64: cpu_to_le64(x) \
457 		)
458 
459 /* LE (e.g. modern) Config space accessors. */
460 #define virtio_cread_le(vdev, structname, member, ptr)			\
461 	do {								\
462 		typeof(((structname*)0)->member) virtio_cread_v;	\
463 									\
464 		might_sleep();						\
465 		/* Sanity check: must match the member's type */	\
466 		typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
467 									\
468 		switch (sizeof(virtio_cread_v)) {			\
469 		case 1:							\
470 		case 2:							\
471 		case 4:							\
472 			vdev->config->get((vdev), 			\
473 					  offsetof(structname, member), \
474 					  &virtio_cread_v,		\
475 					  sizeof(virtio_cread_v));	\
476 			break;						\
477 		default:						\
478 			__virtio_cread_many((vdev), 			\
479 					  offsetof(structname, member), \
480 					  &virtio_cread_v,		\
481 					  1,				\
482 					  sizeof(virtio_cread_v));	\
483 			break;						\
484 		}							\
485 		*(ptr) = virtio_le_to_cpu(virtio_cread_v);		\
486 	} while(0)
487 
488 #define virtio_cwrite_le(vdev, structname, member, ptr)			\
489 	do {								\
490 		typeof(((structname*)0)->member) virtio_cwrite_v =	\
491 			virtio_cpu_to_le(*(ptr), ((structname*)0)->member); \
492 									\
493 		might_sleep();						\
494 		/* Sanity check: must match the member's type */	\
495 		typecheck(typeof(virtio_le_to_cpu(virtio_cwrite_v)), *(ptr)); \
496 									\
497 		vdev->config->set((vdev), offsetof(structname, member),	\
498 				  &virtio_cwrite_v,			\
499 				  sizeof(virtio_cwrite_v));		\
500 	} while(0)
501 
502 
503 /* Read @count fields, @bytes each. */
__virtio_cread_many(struct virtio_device * vdev,unsigned int offset,void * buf,size_t count,size_t bytes)504 static inline void __virtio_cread_many(struct virtio_device *vdev,
505 				       unsigned int offset,
506 				       void *buf, size_t count, size_t bytes)
507 {
508 	u32 old, gen = vdev->config->generation ?
509 		vdev->config->generation(vdev) : 0;
510 	int i;
511 
512 	might_sleep();
513 	do {
514 		old = gen;
515 
516 		for (i = 0; i < count; i++)
517 			vdev->config->get(vdev, offset + bytes * i,
518 					  buf + i * bytes, bytes);
519 
520 		gen = vdev->config->generation ?
521 			vdev->config->generation(vdev) : 0;
522 	} while (gen != old);
523 }
524 
virtio_cread_bytes(struct virtio_device * vdev,unsigned int offset,void * buf,size_t len)525 static inline void virtio_cread_bytes(struct virtio_device *vdev,
526 				      unsigned int offset,
527 				      void *buf, size_t len)
528 {
529 	__virtio_cread_many(vdev, offset, buf, len, 1);
530 }
531 
virtio_cread8(struct virtio_device * vdev,unsigned int offset)532 static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)
533 {
534 	u8 ret;
535 
536 	might_sleep();
537 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
538 	return ret;
539 }
540 
virtio_cwrite8(struct virtio_device * vdev,unsigned int offset,u8 val)541 static inline void virtio_cwrite8(struct virtio_device *vdev,
542 				  unsigned int offset, u8 val)
543 {
544 	might_sleep();
545 	vdev->config->set(vdev, offset, &val, sizeof(val));
546 }
547 
virtio_cread16(struct virtio_device * vdev,unsigned int offset)548 static inline u16 virtio_cread16(struct virtio_device *vdev,
549 				 unsigned int offset)
550 {
551 	__virtio16 ret;
552 
553 	might_sleep();
554 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
555 	return virtio16_to_cpu(vdev, ret);
556 }
557 
virtio_cwrite16(struct virtio_device * vdev,unsigned int offset,u16 val)558 static inline void virtio_cwrite16(struct virtio_device *vdev,
559 				   unsigned int offset, u16 val)
560 {
561 	__virtio16 v;
562 
563 	might_sleep();
564 	v = cpu_to_virtio16(vdev, val);
565 	vdev->config->set(vdev, offset, &v, sizeof(v));
566 }
567 
virtio_cread32(struct virtio_device * vdev,unsigned int offset)568 static inline u32 virtio_cread32(struct virtio_device *vdev,
569 				 unsigned int offset)
570 {
571 	__virtio32 ret;
572 
573 	might_sleep();
574 	vdev->config->get(vdev, offset, &ret, sizeof(ret));
575 	return virtio32_to_cpu(vdev, ret);
576 }
577 
virtio_cwrite32(struct virtio_device * vdev,unsigned int offset,u32 val)578 static inline void virtio_cwrite32(struct virtio_device *vdev,
579 				   unsigned int offset, u32 val)
580 {
581 	__virtio32 v;
582 
583 	might_sleep();
584 	v = cpu_to_virtio32(vdev, val);
585 	vdev->config->set(vdev, offset, &v, sizeof(v));
586 }
587 
virtio_cread64(struct virtio_device * vdev,unsigned int offset)588 static inline u64 virtio_cread64(struct virtio_device *vdev,
589 				 unsigned int offset)
590 {
591 	__virtio64 ret;
592 
593 	__virtio_cread_many(vdev, offset, &ret, 1, sizeof(ret));
594 	return virtio64_to_cpu(vdev, ret);
595 }
596 
virtio_cwrite64(struct virtio_device * vdev,unsigned int offset,u64 val)597 static inline void virtio_cwrite64(struct virtio_device *vdev,
598 				   unsigned int offset, u64 val)
599 {
600 	__virtio64 v;
601 
602 	might_sleep();
603 	v = cpu_to_virtio64(vdev, val);
604 	vdev->config->set(vdev, offset, &v, sizeof(v));
605 }
606 
607 /* Conditional config space accessors. */
608 #define virtio_cread_feature(vdev, fbit, structname, member, ptr)	\
609 	({								\
610 		int _r = 0;						\
611 		if (!virtio_has_feature(vdev, fbit))			\
612 			_r = -ENOENT;					\
613 		else							\
614 			virtio_cread((vdev), structname, member, ptr);	\
615 		_r;							\
616 	})
617 
618 /* Conditional config space accessors. */
619 #define virtio_cread_le_feature(vdev, fbit, structname, member, ptr)	\
620 	({								\
621 		int _r = 0;						\
622 		if (!virtio_has_feature(vdev, fbit))			\
623 			_r = -ENOENT;					\
624 		else							\
625 			virtio_cread_le((vdev), structname, member, ptr); \
626 		_r;							\
627 	})
628 
629 #endif /* _LINUX_VIRTIO_CONFIG_H */
630