xref: /freebsd/usr.sbin/bhyve/virtio.h (revision cc426dd31990b8b50b210efc450e404596548ca1)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2013  Chris Torek <torek @ torek net>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  *
28  * $FreeBSD$
29  */
30 
31 #ifndef	_VIRTIO_H_
32 #define	_VIRTIO_H_
33 
34 /*
35  * These are derived from several virtio specifications.
36  *
37  * Some useful links:
38  *    https://github.com/rustyrussell/virtio-spec
39  *    http://people.redhat.com/pbonzini/virtio-spec.pdf
40  */
41 
42 /*
43  * A virtual device has zero or more "virtual queues" (virtqueue).
44  * Each virtqueue uses at least two 4096-byte pages, laid out thus:
45  *
46  *      +-----------------------------------------------+
47  *      |    "desc":  <N> descriptors, 16 bytes each    |
48  *      |   -----------------------------------------   |
49  *      |   "avail":   2 uint16; <N> uint16; 1 uint16   |
50  *      |   -----------------------------------------   |
51  *      |              pad to 4k boundary               |
52  *      +-----------------------------------------------+
53  *      |   "used": 2 x uint16; <N> elems; 1 uint16     |
54  *      |   -----------------------------------------   |
55  *      |              pad to 4k boundary               |
56  *      +-----------------------------------------------+
57  *
58  * The number <N> that appears here is always a power of two and is
59  * limited to no more than 32768 (as it must fit in a 16-bit field).
60  * If <N> is sufficiently large, the above will occupy more than
61  * two pages.  In any case, all pages must be physically contiguous
62  * within the guest's physical address space.
63  *
64  * The <N> 16-byte "desc" descriptors consist of a 64-bit guest
65  * physical address <addr>, a 32-bit length <len>, a 16-bit
66  * <flags>, and a 16-bit <next> field (all in guest byte order).
67  *
68  * There are three flags that may be set :
69  *	NEXT    descriptor is chained, so use its "next" field
70  *	WRITE   descriptor is for host to write into guest RAM
71  *		(else host is to read from guest RAM)
72  *	INDIRECT   descriptor address field is (guest physical)
73  *		address of a linear array of descriptors
74  *
75  * Unless INDIRECT is set, <len> is the number of bytes that may
76  * be read/written from guest physical address <addr>.  If
77  * INDIRECT is set, WRITE is ignored and <len> provides the length
78  * of the indirect descriptors (and <len> must be a multiple of
79  * 16).  Note that NEXT may still be set in the main descriptor
80  * pointing to the indirect, and should be set in each indirect
81  * descriptor that uses the next descriptor (these should generally
82  * be numbered sequentially).  However, INDIRECT must not be set
83  * in the indirect descriptors.  Upon reaching an indirect descriptor
84  * without a NEXT bit, control returns to the direct descriptors.
85  *
86  * Except inside an indirect, each <next> value must be in the
87  * range [0 .. N) (i.e., the half-open interval).  (Inside an
88  * indirect, each <next> must be in the range [0 .. <len>/16).)
89  *
90  * The "avail" data structures reside in the same pages as the
91  * "desc" structures since both together are used by the device to
92  * pass information to the hypervisor's virtual driver.  These
93  * begin with a 16-bit <flags> field and 16-bit index <idx>, then
94  * have <N> 16-bit <ring> values, followed by one final 16-bit
95  * field <used_event>.  The <N> <ring> entries are simply indices
96  * indices into the descriptor ring (and thus must meet the same
97  * constraints as each <next> value).  However, <idx> is counted
98  * up from 0 (initially) and simply wraps around after 65535; it
99  * is taken mod <N> to find the next available entry.
100  *
101  * The "used" ring occupies a separate page or pages, and contains
102  * values written from the virtual driver back to the guest OS.
103  * This begins with a 16-bit <flags> and 16-bit <idx>, then there
104  * are <N> "vring_used" elements, followed by a 16-bit <avail_event>.
105  * The <N> "vring_used" elements consist of a 32-bit <id> and a
106  * 32-bit <len> (vu_tlen below).  The <id> is simply the index of
107  * the head of a descriptor chain the guest made available
108  * earlier, and the <len> is the number of bytes actually written,
109  * e.g., in the case of a network driver that provided a large
110  * receive buffer but received only a small amount of data.
111  *
112  * The two event fields, <used_event> and <avail_event>, in the
113  * avail and used rings (respectively -- note the reversal!), are
114  * always provided, but are used only if the virtual device
115  * negotiates the VIRTIO_RING_F_EVENT_IDX feature during feature
116  * negotiation.  Similarly, both rings provide a flag --
117  * VRING_AVAIL_F_NO_INTERRUPT and VRING_USED_F_NO_NOTIFY -- in
118  * their <flags> field, indicating that the guest does not need an
119  * interrupt, or that the hypervisor driver does not need a
120  * notify, when descriptors are added to the corresponding ring.
121  * (These are provided only for interrupt optimization and need
122  * not be implemented.)
123  */
124 #define VRING_ALIGN	4096
125 
126 #define VRING_DESC_F_NEXT	(1 << 0)
127 #define VRING_DESC_F_WRITE	(1 << 1)
128 #define VRING_DESC_F_INDIRECT	(1 << 2)
129 
130 struct virtio_desc {			/* AKA vring_desc */
131 	uint64_t	vd_addr;	/* guest physical address */
132 	uint32_t	vd_len;		/* length of scatter/gather seg */
133 	uint16_t	vd_flags;	/* VRING_F_DESC_* */
134 	uint16_t	vd_next;	/* next desc if F_NEXT */
135 } __packed;
136 
137 struct virtio_used {			/* AKA vring_used_elem */
138 	uint32_t	vu_idx;		/* head of used descriptor chain */
139 	uint32_t	vu_tlen;	/* length written-to */
140 } __packed;
141 
142 #define VRING_AVAIL_F_NO_INTERRUPT   1
143 
144 struct vring_avail {
145 	uint16_t	va_flags;	/* VRING_AVAIL_F_* */
146 	uint16_t	va_idx;		/* counts to 65535, then cycles */
147 	uint16_t	va_ring[];	/* size N, reported in QNUM value */
148 /*	uint16_t	va_used_event;	-- after N ring entries */
149 } __packed;
150 
151 #define	VRING_USED_F_NO_NOTIFY		1
152 struct vring_used {
153 	uint16_t	vu_flags;	/* VRING_USED_F_* */
154 	uint16_t	vu_idx;		/* counts to 65535, then cycles */
155 	struct virtio_used vu_ring[];	/* size N */
156 /*	uint16_t	vu_avail_event;	-- after N ring entries */
157 } __packed;
158 
159 /*
160  * The address of any given virtual queue is determined by a single
161  * Page Frame Number register.  The guest writes the PFN into the
162  * PCI config space.  However, a device that has two or more
163  * virtqueues can have a different PFN, and size, for each queue.
164  * The number of queues is determinable via the PCI config space
165  * VTCFG_R_QSEL register.  Writes to QSEL select the queue: 0 means
166  * queue #0, 1 means queue#1, etc.  Once a queue is selected, the
167  * remaining PFN and QNUM registers refer to that queue.
168  *
169  * QNUM is a read-only register containing a nonzero power of two
170  * that indicates the (hypervisor's) queue size.  Or, if reading it
171  * produces zero, the hypervisor does not have a corresponding
172  * queue.  (The number of possible queues depends on the virtual
173  * device.  The block device has just one; the network device
174  * provides either two -- 0 = receive, 1 = transmit -- or three,
175  * with 2 = control.)
176  *
177  * PFN is a read/write register giving the physical page address of
178  * the virtqueue in guest memory (the guest must allocate enough space
179  * based on the hypervisor's provided QNUM).
180  *
181  * QNOTIFY is effectively write-only: when the guest writes a queue
182  * number to the register, the hypervisor should scan the specified
183  * virtqueue. (Reading QNOTIFY currently always gets 0).
184  */
185 
186 /*
187  * PFN register shift amount
188  */
189 #define	VRING_PFN		12
190 
191 /*
192  * Virtio device types
193  *
194  * XXX Should really be merged with <dev/virtio/virtio.h> defines
195  */
196 #define	VIRTIO_TYPE_NET		1
197 #define	VIRTIO_TYPE_BLOCK	2
198 #define	VIRTIO_TYPE_CONSOLE	3
199 #define	VIRTIO_TYPE_ENTROPY	4
200 #define	VIRTIO_TYPE_BALLOON	5
201 #define	VIRTIO_TYPE_IOMEMORY	6
202 #define	VIRTIO_TYPE_RPMSG	7
203 #define	VIRTIO_TYPE_SCSI	8
204 #define	VIRTIO_TYPE_9P		9
205 
206 /* experimental IDs start at 65535 and work down */
207 
208 /*
209  * PCI vendor/device IDs
210  */
211 #define	VIRTIO_VENDOR		0x1AF4
212 #define	VIRTIO_DEV_NET		0x1000
213 #define	VIRTIO_DEV_BLOCK	0x1001
214 #define	VIRTIO_DEV_CONSOLE	0x1003
215 #define	VIRTIO_DEV_RANDOM	0x1005
216 #define	VIRTIO_DEV_SCSI		0x1008
217 
218 /*
219  * PCI config space constants.
220  *
221  * If MSI-X is enabled, the ISR register is generally not used,
222  * and the configuration vector and queue vector appear at offsets
223  * 20 and 22 with the remaining configuration registers at 24.
224  * If MSI-X is not enabled, those two registers disappear and
225  * the remaining configuration registers start at offset 20.
226  */
227 #define	VTCFG_R_HOSTCAP		0
228 #define	VTCFG_R_GUESTCAP	4
229 #define	VTCFG_R_PFN		8
230 #define	VTCFG_R_QNUM		12
231 #define	VTCFG_R_QSEL		14
232 #define	VTCFG_R_QNOTIFY		16
233 #define	VTCFG_R_STATUS		18
234 #define	VTCFG_R_ISR		19
235 #define	VTCFG_R_CFGVEC		20
236 #define	VTCFG_R_QVEC		22
237 #define	VTCFG_R_CFG0		20	/* No MSI-X */
238 #define	VTCFG_R_CFG1		24	/* With MSI-X */
239 #define	VTCFG_R_MSIX		20
240 
241 /*
242  * Bits in VTCFG_R_STATUS.  Guests need not actually set any of these,
243  * but a guest writing 0 to this register means "please reset".
244  */
245 #define	VTCFG_STATUS_ACK	0x01	/* guest OS has acknowledged dev */
246 #define	VTCFG_STATUS_DRIVER	0x02	/* guest OS driver is loaded */
247 #define	VTCFG_STATUS_DRIVER_OK	0x04	/* guest OS driver ready */
248 #define	VTCFG_STATUS_FAILED	0x80	/* guest has given up on this dev */
249 
250 /*
251  * Bits in VTCFG_R_ISR.  These apply only if not using MSI-X.
252  *
253  * (We don't [yet?] ever use CONF_CHANGED.)
254  */
255 #define	VTCFG_ISR_QUEUES	0x01	/* re-scan queues */
256 #define	VTCFG_ISR_CONF_CHANGED	0x80	/* configuration changed */
257 
258 #define	VIRTIO_MSI_NO_VECTOR	0xFFFF
259 
260 /*
261  * Feature flags.
262  * Note: bits 0 through 23 are reserved to each device type.
263  */
264 #define	VIRTIO_F_NOTIFY_ON_EMPTY	(1 << 24)
265 #define	VIRTIO_RING_F_INDIRECT_DESC	(1 << 28)
266 #define	VIRTIO_RING_F_EVENT_IDX		(1 << 29)
267 
268 /* From section 2.3, "Virtqueue Configuration", of the virtio specification */
269 static inline size_t
270 vring_size(u_int qsz)
271 {
272 	size_t size;
273 
274 	/* constant 3 below = va_flags, va_idx, va_used_event */
275 	size = sizeof(struct virtio_desc) * qsz + sizeof(uint16_t) * (3 + qsz);
276 	size = roundup2(size, VRING_ALIGN);
277 
278 	/* constant 3 below = vu_flags, vu_idx, vu_avail_event */
279 	size += sizeof(uint16_t) * 3 + sizeof(struct virtio_used) * qsz;
280 	size = roundup2(size, VRING_ALIGN);
281 
282 	return (size);
283 }
284 
285 struct vmctx;
286 struct pci_devinst;
287 struct vqueue_info;
288 
289 /*
290  * A virtual device, with some number (possibly 0) of virtual
291  * queues and some size (possibly 0) of configuration-space
292  * registers private to the device.  The virtio_softc should come
293  * at the front of each "derived class", so that a pointer to the
294  * virtio_softc is also a pointer to the more specific, derived-
295  * from-virtio driver's softc.
296  *
297  * Note: inside each hypervisor virtio driver, changes to these
298  * data structures must be locked against other threads, if any.
299  * Except for PCI config space register read/write, we assume each
300  * driver does the required locking, but we need a pointer to the
301  * lock (if there is one) for PCI config space read/write ops.
302  *
303  * When the guest reads or writes the device's config space, the
304  * generic layer checks for operations on the special registers
305  * described above.  If the offset of the register(s) being read
306  * or written is past the CFG area (CFG0 or CFG1), the request is
307  * passed on to the virtual device, after subtracting off the
308  * generic-layer size.  (So, drivers can just use the offset as
309  * an offset into "struct config", for instance.)
310  *
311  * (The virtio layer also makes sure that the read or write is to/
312  * from a "good" config offset, hence vc_cfgsize, and on BAR #0.
313  * However, the driver must verify the read or write size and offset
314  * and that no one is writing a readonly register.)
315  *
316  * The BROKED flag ("this thing done gone and broked") is for future
317  * use.
318  */
319 #define	VIRTIO_USE_MSIX		0x01
320 #define	VIRTIO_EVENT_IDX	0x02	/* use the event-index values */
321 #define	VIRTIO_BROKED		0x08	/* ??? */
322 
323 struct virtio_softc {
324 	struct virtio_consts *vs_vc;	/* constants (see below) */
325 	int	vs_flags;		/* VIRTIO_* flags from above */
326 	pthread_mutex_t *vs_mtx;	/* POSIX mutex, if any */
327 	struct pci_devinst *vs_pi;	/* PCI device instance */
328 	uint32_t vs_negotiated_caps;	/* negotiated capabilities */
329 	struct vqueue_info *vs_queues;	/* one per vc_nvq */
330 	int	vs_curq;		/* current queue */
331 	uint8_t	vs_status;		/* value from last status write */
332 	uint8_t	vs_isr;			/* ISR flags, if not MSI-X */
333 	uint16_t vs_msix_cfg_idx;	/* MSI-X vector for config event */
334 };
335 
336 #define	VS_LOCK(vs)							\
337 do {									\
338 	if (vs->vs_mtx)							\
339 		pthread_mutex_lock(vs->vs_mtx);				\
340 } while (0)
341 
342 #define	VS_UNLOCK(vs)							\
343 do {									\
344 	if (vs->vs_mtx)							\
345 		pthread_mutex_unlock(vs->vs_mtx);			\
346 } while (0)
347 
348 struct virtio_consts {
349 	const char *vc_name;		/* name of driver (for diagnostics) */
350 	int	vc_nvq;			/* number of virtual queues */
351 	size_t	vc_cfgsize;		/* size of dev-specific config regs */
352 	void	(*vc_reset)(void *);	/* called on virtual device reset */
353 	void	(*vc_qnotify)(void *, struct vqueue_info *);
354 					/* called on QNOTIFY if no VQ notify */
355 	int	(*vc_cfgread)(void *, int, int, uint32_t *);
356 					/* called to read config regs */
357 	int	(*vc_cfgwrite)(void *, int, int, uint32_t);
358 					/* called to write config regs */
359 	void    (*vc_apply_features)(void *, uint64_t);
360 				/* called to apply negotiated features */
361 	uint64_t vc_hv_caps;		/* hypervisor-provided capabilities */
362 };
363 
364 /*
365  * Data structure allocated (statically) per virtual queue.
366  *
367  * Drivers may change vq_qsize after a reset.  When the guest OS
368  * requests a device reset, the hypervisor first calls
369  * vs->vs_vc->vc_reset(); then the data structure below is
370  * reinitialized (for each virtqueue: vs->vs_vc->vc_nvq).
371  *
372  * The remaining fields should only be fussed-with by the generic
373  * code.
374  *
375  * Note: the addresses of vq_desc, vq_avail, and vq_used are all
376  * computable from each other, but it's a lot simpler if we just
377  * keep a pointer to each one.  The event indices are similarly
378  * (but more easily) computable, and this time we'll compute them:
379  * they're just XX_ring[N].
380  */
381 #define	VQ_ALLOC	0x01	/* set once we have a pfn */
382 #define	VQ_BROKED	0x02	/* ??? */
383 struct vqueue_info {
384 	uint16_t vq_qsize;	/* size of this queue (a power of 2) */
385 	void	(*vq_notify)(void *, struct vqueue_info *);
386 				/* called instead of vc_notify, if not NULL */
387 
388 	struct virtio_softc *vq_vs;	/* backpointer to softc */
389 	uint16_t vq_num;	/* we're the num'th queue in the softc */
390 
391 	uint16_t vq_flags;	/* flags (see above) */
392 	uint16_t vq_last_avail;	/* a recent value of vq_avail->va_idx */
393 	uint16_t vq_save_used;	/* saved vq_used->vu_idx; see vq_endchains */
394 	uint16_t vq_msix_idx;	/* MSI-X index, or VIRTIO_MSI_NO_VECTOR */
395 
396 	uint32_t vq_pfn;	/* PFN of virt queue (not shifted!) */
397 
398 	volatile struct virtio_desc *vq_desc;	/* descriptor array */
399 	volatile struct vring_avail *vq_avail;	/* the "avail" ring */
400 	volatile struct vring_used *vq_used;	/* the "used" ring */
401 
402 };
403 /* as noted above, these are sort of backwards, name-wise */
404 #define VQ_AVAIL_EVENT_IDX(vq) \
405 	(*(volatile uint16_t *)&(vq)->vq_used->vu_ring[(vq)->vq_qsize])
406 #define VQ_USED_EVENT_IDX(vq) \
407 	((vq)->vq_avail->va_ring[(vq)->vq_qsize])
408 
409 /*
410  * Is this ring ready for I/O?
411  */
412 static inline int
413 vq_ring_ready(struct vqueue_info *vq)
414 {
415 
416 	return (vq->vq_flags & VQ_ALLOC);
417 }
418 
419 /*
420  * Are there "available" descriptors?  (This does not count
421  * how many, just returns True if there are some.)
422  */
423 static inline int
424 vq_has_descs(struct vqueue_info *vq)
425 {
426 
427 	return (vq_ring_ready(vq) && vq->vq_last_avail !=
428 	    vq->vq_avail->va_idx);
429 }
430 
431 /*
432  * Deliver an interrupt to guest on the given virtual queue
433  * (if possible, or a generic MSI interrupt if not using MSI-X).
434  */
435 static inline void
436 vq_interrupt(struct virtio_softc *vs, struct vqueue_info *vq)
437 {
438 
439 	if (pci_msix_enabled(vs->vs_pi))
440 		pci_generate_msix(vs->vs_pi, vq->vq_msix_idx);
441 	else {
442 		VS_LOCK(vs);
443 		vs->vs_isr |= VTCFG_ISR_QUEUES;
444 		pci_generate_msi(vs->vs_pi, 0);
445 		pci_lintr_assert(vs->vs_pi);
446 		VS_UNLOCK(vs);
447 	}
448 }
449 
450 struct iovec;
451 void	vi_softc_linkup(struct virtio_softc *vs, struct virtio_consts *vc,
452 			void *dev_softc, struct pci_devinst *pi,
453 			struct vqueue_info *queues);
454 int	vi_intr_init(struct virtio_softc *vs, int barnum, int use_msix);
455 void	vi_reset_dev(struct virtio_softc *);
456 void	vi_set_io_bar(struct virtio_softc *, int);
457 
458 int	vq_getchain(struct vqueue_info *vq, uint16_t *pidx,
459 		    struct iovec *iov, int n_iov, uint16_t *flags);
460 void	vq_retchain(struct vqueue_info *vq);
461 void	vq_relchain(struct vqueue_info *vq, uint16_t idx, uint32_t iolen);
462 void	vq_endchains(struct vqueue_info *vq, int used_all_avail);
463 
464 uint64_t vi_pci_read(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
465 		     int baridx, uint64_t offset, int size);
466 void	vi_pci_write(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
467 		     int baridx, uint64_t offset, int size, uint64_t value);
468 #endif	/* _VIRTIO_H_ */
469