2 * Lguest guests use a very simple method to describe devices. It's a
3 * series of device descriptors contained just above the top of normal Guest
6 * We use the standard "virtio" device infrastructure, which provides us with a
7 * console, a network and a block driver. Each one expects some configuration
8 * information and a "virtqueue" or two to send and receive data.
10 #include <linux/init.h>
11 #include <linux/bootmem.h>
12 #include <linux/lguest_launcher.h>
13 #include <linux/virtio.h>
14 #include <linux/virtio_config.h>
15 #include <linux/interrupt.h>
16 #include <linux/virtio_ring.h>
17 #include <linux/err.h>
18 #include <linux/export.h>
19 #include <linux/slab.h>
21 #include <asm/paravirt.h>
22 #include <asm/lguest_hcall.h>
24 /* The pointer to our (page) of device descriptions. */
25 static void *lguest_devices
;
28 * For Guests, device memory can be used as normal memory, so we cast away the
29 * __iomem to quieten sparse.
31 static inline void *lguest_map(unsigned long phys_addr
, unsigned long pages
)
33 return (__force
void *)ioremap_cache(phys_addr
, PAGE_SIZE
*pages
);
36 static inline void lguest_unmap(void *addr
)
38 iounmap((__force
void __iomem
*)addr
);
42 * Each lguest device is just a virtio device plus a pointer to its entry
43 * in the lguest_devices page.
45 struct lguest_device
{
46 struct virtio_device vdev
;
48 /* The entry in the lguest_devices page for this device. */
49 struct lguest_device_desc
*desc
;
53 * Since the virtio infrastructure hands us a pointer to the virtio_device all
54 * the time, it helps to have a curt macro to get a pointer to the struct
55 * lguest_device it's enclosed in.
57 #define to_lgdev(vd) container_of(vd, struct lguest_device, vdev)
60 * Device configurations
62 * The configuration information for a device consists of one or more
63 * virtqueues, a feature bitmap, and some configuration bytes. The
64 * configuration bytes don't really matter to us: the Launcher sets them up, and
65 * the driver will look at them during setup.
67 * A convenient routine to return the device's virtqueue config array:
68 * immediately after the descriptor.
70 static struct lguest_vqconfig
*lg_vq(const struct lguest_device_desc
*desc
)
72 return (void *)(desc
+ 1);
75 /* The features come immediately after the virtqueues. */
76 static u8
*lg_features(const struct lguest_device_desc
*desc
)
78 return (void *)(lg_vq(desc
) + desc
->num_vq
);
81 /* The config space comes after the two feature bitmasks. */
82 static u8
*lg_config(const struct lguest_device_desc
*desc
)
84 return lg_features(desc
) + desc
->feature_len
* 2;
87 /* The total size of the config page used by this device (incl. desc) */
88 static unsigned desc_size(const struct lguest_device_desc
*desc
)
91 + desc
->num_vq
* sizeof(struct lguest_vqconfig
)
92 + desc
->feature_len
* 2
96 /* This gets the device's feature bits. */
97 static u32
lg_get_features(struct virtio_device
*vdev
)
101 struct lguest_device_desc
*desc
= to_lgdev(vdev
)->desc
;
102 u8
*in_features
= lg_features(desc
);
104 /* We do this the slow but generic way. */
105 for (i
= 0; i
< min(desc
->feature_len
* 8, 32); i
++)
106 if (in_features
[i
/ 8] & (1 << (i
% 8)))
107 features
|= (1 << i
);
113 * To notify on reset or feature finalization, we (ab)use the NOTIFY
114 * hypercall, with the descriptor address of the device.
116 static void status_notify(struct virtio_device
*vdev
)
118 unsigned long offset
= (void *)to_lgdev(vdev
)->desc
- lguest_devices
;
120 hcall(LHCALL_NOTIFY
, (max_pfn
<< PAGE_SHIFT
) + offset
, 0, 0, 0);
124 * The virtio core takes the features the Host offers, and copies the ones
125 * supported by the driver into the vdev->features array. Once that's all
126 * sorted out, this routine is called so we can tell the Host which features we
127 * understand and accept.
129 static void lg_finalize_features(struct virtio_device
*vdev
)
131 unsigned int i
, bits
;
132 struct lguest_device_desc
*desc
= to_lgdev(vdev
)->desc
;
133 /* Second half of bitmap is features we accept. */
134 u8
*out_features
= lg_features(desc
) + desc
->feature_len
;
136 /* Give virtio_ring a chance to accept features. */
137 vring_transport_features(vdev
);
140 * The vdev->feature array is a Linux bitmask: this isn't the same as a
141 * the simple array of bits used by lguest devices for features. So we
142 * do this slow, manual conversion which is completely general.
144 memset(out_features
, 0, desc
->feature_len
);
145 bits
= min_t(unsigned, desc
->feature_len
, sizeof(vdev
->features
)) * 8;
146 for (i
= 0; i
< bits
; i
++) {
147 if (test_bit(i
, vdev
->features
))
148 out_features
[i
/ 8] |= (1 << (i
% 8));
151 /* Tell Host we've finished with this device's feature negotiation */
155 /* Once they've found a field, getting a copy of it is easy. */
156 static void lg_get(struct virtio_device
*vdev
, unsigned int offset
,
157 void *buf
, unsigned len
)
159 struct lguest_device_desc
*desc
= to_lgdev(vdev
)->desc
;
161 /* Check they didn't ask for more than the length of the config! */
162 BUG_ON(offset
+ len
> desc
->config_len
);
163 memcpy(buf
, lg_config(desc
) + offset
, len
);
166 /* Setting the contents is also trivial. */
167 static void lg_set(struct virtio_device
*vdev
, unsigned int offset
,
168 const void *buf
, unsigned len
)
170 struct lguest_device_desc
*desc
= to_lgdev(vdev
)->desc
;
172 /* Check they didn't ask for more than the length of the config! */
173 BUG_ON(offset
+ len
> desc
->config_len
);
174 memcpy(lg_config(desc
) + offset
, buf
, len
);
178 * The operations to get and set the status word just access the status field
179 * of the device descriptor.
181 static u8
lg_get_status(struct virtio_device
*vdev
)
183 return to_lgdev(vdev
)->desc
->status
;
186 static void lg_set_status(struct virtio_device
*vdev
, u8 status
)
189 to_lgdev(vdev
)->desc
->status
= status
;
191 /* Tell Host immediately if we failed. */
192 if (status
& VIRTIO_CONFIG_S_FAILED
)
196 static void lg_reset(struct virtio_device
*vdev
)
198 /* 0 status means "reset" */
199 to_lgdev(vdev
)->desc
->status
= 0;
206 * The other piece of infrastructure virtio needs is a "virtqueue": a way of
207 * the Guest device registering buffers for the other side to read from or
208 * write into (ie. send and receive buffers). Each device can have multiple
209 * virtqueues: for example the console driver uses one queue for sending and
210 * another for receiving.
212 * Fortunately for us, a very fast shared-memory-plus-descriptors virtqueue
213 * already exists in virtio_ring.c. We just need to connect it up.
215 * We start with the information we need to keep about each virtqueue.
218 /*D:140 This is the information we remember about each virtqueue. */
219 struct lguest_vq_info
{
220 /* A copy of the information contained in the device config. */
221 struct lguest_vqconfig config
;
223 /* The address where we mapped the virtio ring, so we can unmap it. */
228 * When the virtio_ring code wants to prod the Host, it calls us here and we
229 * make a hypercall. We hand the physical address of the virtqueue so the Host
230 * knows which virtqueue we're talking about.
232 static void lg_notify(struct virtqueue
*vq
)
235 * We store our virtqueue information in the "priv" pointer of the
236 * virtqueue structure.
238 struct lguest_vq_info
*lvq
= vq
->priv
;
240 hcall(LHCALL_NOTIFY
, lvq
->config
.pfn
<< PAGE_SHIFT
, 0, 0, 0);
243 /* An extern declaration inside a C file is bad form. Don't do it. */
244 extern void lguest_setup_irq(unsigned int irq
);
247 * This routine finds the Nth virtqueue described in the configuration of
248 * this device and sets it up.
250 * This is kind of an ugly duckling. It'd be nicer to have a standard
251 * representation of a virtqueue in the configuration space, but it seems that
252 * everyone wants to do it differently. The KVM coders want the Guest to
253 * allocate its own pages and tell the Host where they are, but for lguest it's
254 * simpler for the Host to simply tell us where the pages are.
256 static struct virtqueue
*lg_find_vq(struct virtio_device
*vdev
,
258 void (*callback
)(struct virtqueue
*vq
),
261 struct lguest_device
*ldev
= to_lgdev(vdev
);
262 struct lguest_vq_info
*lvq
;
263 struct virtqueue
*vq
;
266 /* We must have this many virtqueues. */
267 if (index
>= ldev
->desc
->num_vq
)
268 return ERR_PTR(-ENOENT
);
270 lvq
= kmalloc(sizeof(*lvq
), GFP_KERNEL
);
272 return ERR_PTR(-ENOMEM
);
275 * Make a copy of the "struct lguest_vqconfig" entry, which sits after
276 * the descriptor. We need a copy because the config space might not
277 * be aligned correctly.
279 memcpy(&lvq
->config
, lg_vq(ldev
->desc
)+index
, sizeof(lvq
->config
));
281 printk("Mapping virtqueue %i addr %lx\n", index
,
282 (unsigned long)lvq
->config
.pfn
<< PAGE_SHIFT
);
283 /* Figure out how many pages the ring will take, and map that memory */
284 lvq
->pages
= lguest_map((unsigned long)lvq
->config
.pfn
<< PAGE_SHIFT
,
285 DIV_ROUND_UP(vring_size(lvq
->config
.num
,
294 * OK, tell virtio_ring.c to set up a virtqueue now we know its size
295 * and we've got a pointer to its pages.
297 vq
= vring_new_virtqueue(lvq
->config
.num
, LGUEST_VRING_ALIGN
,
298 vdev
, lvq
->pages
, lg_notify
, callback
, name
);
304 /* Make sure the interrupt is allocated. */
305 lguest_setup_irq(lvq
->config
.irq
);
308 * Tell the interrupt for this virtqueue to go to the virtio_ring
311 * FIXME: We used to have a flag for the Host to tell us we could use
312 * the interrupt as a source of randomness: it'd be nice to have that
315 err
= request_irq(lvq
->config
.irq
, vring_interrupt
, IRQF_SHARED
,
316 dev_name(&vdev
->dev
), vq
);
321 * Last of all we hook up our 'struct lguest_vq_info" to the
322 * virtqueue's priv pointer.
328 vring_del_virtqueue(vq
);
330 lguest_unmap(lvq
->pages
);
337 /* Cleaning up a virtqueue is easy */
338 static void lg_del_vq(struct virtqueue
*vq
)
340 struct lguest_vq_info
*lvq
= vq
->priv
;
342 /* Release the interrupt */
343 free_irq(lvq
->config
.irq
, vq
);
344 /* Tell virtio_ring.c to free the virtqueue. */
345 vring_del_virtqueue(vq
);
346 /* Unmap the pages containing the ring. */
347 lguest_unmap(lvq
->pages
);
348 /* Free our own queue information. */
352 static void lg_del_vqs(struct virtio_device
*vdev
)
354 struct virtqueue
*vq
, *n
;
356 list_for_each_entry_safe(vq
, n
, &vdev
->vqs
, list
)
360 static int lg_find_vqs(struct virtio_device
*vdev
, unsigned nvqs
,
361 struct virtqueue
*vqs
[],
362 vq_callback_t
*callbacks
[],
365 struct lguest_device
*ldev
= to_lgdev(vdev
);
368 /* We must have this many virtqueues. */
369 if (nvqs
> ldev
->desc
->num_vq
)
372 for (i
= 0; i
< nvqs
; ++i
) {
373 vqs
[i
] = lg_find_vq(vdev
, i
, callbacks
[i
], names
[i
]);
381 return PTR_ERR(vqs
[i
]);
384 /* The ops structure which hooks everything together. */
385 static struct virtio_config_ops lguest_config_ops
= {
386 .get_features
= lg_get_features
,
387 .finalize_features
= lg_finalize_features
,
390 .get_status
= lg_get_status
,
391 .set_status
= lg_set_status
,
393 .find_vqs
= lg_find_vqs
,
394 .del_vqs
= lg_del_vqs
,
398 * The root device for the lguest virtio devices. This makes them appear as
399 * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2.
401 static struct device
*lguest_root
;
404 * This is the core of the lguest bus: actually adding a new device.
405 * It's a separate function because it's neater that way, and because an
406 * earlier version of the code supported hotplug and unplug. They were removed
407 * early on because they were never used.
409 * As Andrew Tridgell says, "Untested code is buggy code".
411 * It's worth reading this carefully: we start with a pointer to the new device
412 * descriptor in the "lguest_devices" page, and the offset into the device
413 * descriptor page so we can uniquely identify it if things go badly wrong.
415 static void add_lguest_device(struct lguest_device_desc
*d
,
418 struct lguest_device
*ldev
;
420 /* Start with zeroed memory; Linux's device layer counts on it. */
421 ldev
= kzalloc(sizeof(*ldev
), GFP_KERNEL
);
423 printk(KERN_EMERG
"Cannot allocate lguest dev %u type %u\n",
428 /* This devices' parent is the lguest/ dir. */
429 ldev
->vdev
.dev
.parent
= lguest_root
;
431 * The device type comes straight from the descriptor. There's also a
432 * device vendor field in the virtio_device struct, which we leave as
435 ldev
->vdev
.id
.device
= d
->type
;
437 * We have a simple set of routines for querying the device's
438 * configuration information and setting its status.
440 ldev
->vdev
.config
= &lguest_config_ops
;
441 /* And we remember the device's descriptor for lguest_config_ops. */
445 * register_virtio_device() sets up the generic fields for the struct
446 * virtio_device and calls device_register(). This makes the bus
447 * infrastructure look for a matching driver.
449 if (register_virtio_device(&ldev
->vdev
) != 0) {
450 printk(KERN_ERR
"Failed to register lguest dev %u type %u\n",
457 * scan_devices() simply iterates through the device page. The type 0 is
458 * reserved to mean "end of devices".
460 static void scan_devices(void)
463 struct lguest_device_desc
*d
;
465 /* We start at the page beginning, and skip over each entry. */
466 for (i
= 0; i
< PAGE_SIZE
; i
+= desc_size(d
)) {
467 d
= lguest_devices
+ i
;
469 /* Once we hit a zero, stop. */
473 printk("Device at %i has size %u\n", i
, desc_size(d
));
474 add_lguest_device(d
, i
);
479 * Fairly early in boot, lguest_devices_init() is called to set up the
480 * lguest device infrastructure. We check that we are a Guest by checking
481 * pv_info.name: there are other ways of checking, but this seems most
484 * So we can access the "struct lguest_device_desc"s easily, we map that memory
485 * and store the pointer in the global "lguest_devices". Then we register a
486 * root device from which all our devices will hang (this seems to be the
487 * correct sysfs incantation).
489 * Finally we call scan_devices() which adds all the devices found in the
490 * lguest_devices page.
492 static int __init
lguest_devices_init(void)
494 if (strcmp(pv_info
.name
, "lguest") != 0)
497 lguest_root
= root_device_register("lguest");
498 if (IS_ERR(lguest_root
))
499 panic("Could not register lguest root");
501 /* Devices are in a single page above top of "normal" mem */
502 lguest_devices
= lguest_map(max_pfn
<<PAGE_SHIFT
, 1);
507 /* We do this after core stuff, but before the drivers. */
508 postcore_initcall(lguest_devices_init
);
511 * At this point in the journey we used to now wade through the lguest
512 * devices themselves: net, block and console. Since they're all now virtio
513 * devices rather than lguest-specific, I've decided to ignore them. Mostly,
514 * they're kind of boring. But this does mean you'll never experience the
515 * thrill of reading the forbidden love scene buried deep in the block driver.
517 * "make Launcher" beckons, where we answer questions like "Where do Guests
518 * come from?", and "What do you do when someone asks for optimization?".