1/*P:050 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 4 * memory. 5 * 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. 9:*/ 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> 20#include <asm/io.h> 21#include <asm/paravirt.h> 22#include <asm/lguest_hcall.h> 23 24/* The pointer to our (page) of device descriptions. */ 25static void *lguest_devices; 26 27/* 28 * For Guests, device memory can be used as normal memory, so we cast away the 29 * __iomem to quieten sparse. 30 */ 31static inline void *lguest_map(unsigned long phys_addr, unsigned long pages) 32{ 33 return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages); 34} 35 36static inline void lguest_unmap(void *addr) 37{ 38 iounmap((__force void __iomem *)addr); 39} 40 41/*D:100 42 * Each lguest device is just a virtio device plus a pointer to its entry 43 * in the lguest_devices page. 44 */ 45struct lguest_device { 46 struct virtio_device vdev; 47 48 /* The entry in the lguest_devices page for this device. */ 49 struct lguest_device_desc *desc; 50}; 51 52/* 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. 56 */ 57#define to_lgdev(vd) container_of(vd, struct lguest_device, vdev) 58 59/*D:130 60 * Device configurations 61 * 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. 66 * 67 * A convenient routine to return the device's virtqueue config array: 68 * immediately after the descriptor. 69 */ 70static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc) 71{ 72 return (void *)(desc + 1); 73} 74 75/* The features come immediately after the virtqueues. */ 76static u8 *lg_features(const struct lguest_device_desc *desc) 77{ 78 return (void *)(lg_vq(desc) + desc->num_vq); 79} 80 81/* The config space comes after the two feature bitmasks. */ 82static u8 *lg_config(const struct lguest_device_desc *desc) 83{ 84 return lg_features(desc) + desc->feature_len * 2; 85} 86 87/* The total size of the config page used by this device (incl. desc) */ 88static unsigned desc_size(const struct lguest_device_desc *desc) 89{ 90 return sizeof(*desc) 91 + desc->num_vq * sizeof(struct lguest_vqconfig) 92 + desc->feature_len * 2 93 + desc->config_len; 94} 95 96/* This gets the device's feature bits. */ 97static u32 lg_get_features(struct virtio_device *vdev) 98{ 99 unsigned int i; 100 u32 features = 0; 101 struct lguest_device_desc *desc = to_lgdev(vdev)->desc; 102 u8 *in_features = lg_features(desc); 103 104 /* 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); 108 109 return features; 110} 111 112/* 113 * To notify on reset or feature finalization, we (ab)use the NOTIFY 114 * hypercall, with the descriptor address of the device. 115 */ 116static void status_notify(struct virtio_device *vdev) 117{ 118 unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices; 119 120 hcall(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset, 0, 0, 0); 121} 122 123/* 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. 128 */ 129static void lg_finalize_features(struct virtio_device *vdev) 130{ 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; 135 136 /* Give virtio_ring a chance to accept features. */ 137 vring_transport_features(vdev); 138 139 /* 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. 143 */ 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)); 149 } 150 151 /* Tell Host we've finished with this device's feature negotiation */ 152 status_notify(vdev); 153} 154 155/* Once they've found a field, getting a copy of it is easy. */ 156static void lg_get(struct virtio_device *vdev, unsigned int offset, 157 void *buf, unsigned len) 158{ 159 struct lguest_device_desc *desc = to_lgdev(vdev)->desc; 160 161 /* 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); 164} 165 166/* Setting the contents is also trivial. */ 167static void lg_set(struct virtio_device *vdev, unsigned int offset, 168 const void *buf, unsigned len) 169{ 170 struct lguest_device_desc *desc = to_lgdev(vdev)->desc; 171 172 /* 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); 175} 176 177/* 178 * The operations to get and set the status word just access the status field 179 * of the device descriptor. 180 */ 181static u8 lg_get_status(struct virtio_device *vdev) 182{ 183 return to_lgdev(vdev)->desc->status; 184} 185 186static void lg_set_status(struct virtio_device *vdev, u8 status) 187{ 188 BUG_ON(!status); 189 to_lgdev(vdev)->desc->status = status; 190 191 /* Tell Host immediately if we failed. */ 192 if (status & VIRTIO_CONFIG_S_FAILED) 193 status_notify(vdev); 194} 195 196static void lg_reset(struct virtio_device *vdev) 197{ 198 /* 0 status means "reset" */ 199 to_lgdev(vdev)->desc->status = 0; 200 status_notify(vdev); 201} 202 203/* 204 * Virtqueues 205 * 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. 211 * 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. 214 * 215 * We start with the information we need to keep about each virtqueue. 216 */ 217 218/*D:140 This is the information we remember about each virtqueue. */ 219struct lguest_vq_info { 220 /* A copy of the information contained in the device config. */ 221 struct lguest_vqconfig config; 222 223 /* The address where we mapped the virtio ring, so we can unmap it. */ 224 void *pages; 225}; 226 227/* 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. 231 */ 232static bool lg_notify(struct virtqueue *vq) 233{ 234 /* 235 * We store our virtqueue information in the "priv" pointer of the 236 * virtqueue structure. 237 */ 238 struct lguest_vq_info *lvq = vq->priv; 239 240 hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0, 0); 241 return true; 242} 243 244/* An extern declaration inside a C file is bad form. Don't do it. */ 245extern int lguest_setup_irq(unsigned int irq); 246 247/* 248 * This routine finds the Nth virtqueue described in the configuration of 249 * this device and sets it up. 250 * 251 * This is kind of an ugly duckling. It'd be nicer to have a standard 252 * representation of a virtqueue in the configuration space, but it seems that 253 * everyone wants to do it differently. The KVM coders want the Guest to 254 * allocate its own pages and tell the Host where they are, but for lguest it's 255 * simpler for the Host to simply tell us where the pages are. 256 */ 257static struct virtqueue *lg_find_vq(struct virtio_device *vdev, 258 unsigned index, 259 void (*callback)(struct virtqueue *vq), 260 const char *name) 261{ 262 struct lguest_device *ldev = to_lgdev(vdev); 263 struct lguest_vq_info *lvq; 264 struct virtqueue *vq; 265 int err; 266 267 if (!name) 268 return NULL; 269 270 /* We must have this many virtqueues. */ 271 if (index >= ldev->desc->num_vq) 272 return ERR_PTR(-ENOENT); 273 274 lvq = kmalloc(sizeof(*lvq), GFP_KERNEL); 275 if (!lvq) 276 return ERR_PTR(-ENOMEM); 277 278 /* 279 * Make a copy of the "struct lguest_vqconfig" entry, which sits after 280 * the descriptor. We need a copy because the config space might not 281 * be aligned correctly. 282 */ 283 memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config)); 284 285 printk("Mapping virtqueue %i addr %lx\n", index, 286 (unsigned long)lvq->config.pfn << PAGE_SHIFT); 287 /* Figure out how many pages the ring will take, and map that memory */ 288 lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT, 289 DIV_ROUND_UP(vring_size(lvq->config.num, 290 LGUEST_VRING_ALIGN), 291 PAGE_SIZE)); 292 if (!lvq->pages) { 293 err = -ENOMEM; 294 goto free_lvq; 295 } 296 297 /* 298 * OK, tell virtio_ring.c to set up a virtqueue now we know its size 299 * and we've got a pointer to its pages. Note that we set weak_barriers 300 * to 'true': the host just a(nother) SMP CPU, so we only need inter-cpu 301 * barriers. 302 */ 303 vq = vring_new_virtqueue(index, lvq->config.num, LGUEST_VRING_ALIGN, vdev, 304 true, lvq->pages, lg_notify, callback, name); 305 if (!vq) { 306 err = -ENOMEM; 307 goto unmap; 308 } 309 310 /* Make sure the interrupt is allocated. */ 311 err = lguest_setup_irq(lvq->config.irq); 312 if (err) 313 goto destroy_vring; 314 315 /* 316 * Tell the interrupt for this virtqueue to go to the virtio_ring 317 * interrupt handler. 318 * 319 * FIXME: We used to have a flag for the Host to tell us we could use 320 * the interrupt as a source of randomness: it'd be nice to have that 321 * back. 322 */ 323 err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED, 324 dev_name(&vdev->dev), vq); 325 if (err) 326 goto free_desc; 327 328 /* 329 * Last of all we hook up our 'struct lguest_vq_info" to the 330 * virtqueue's priv pointer. 331 */ 332 vq->priv = lvq; 333 return vq; 334 335free_desc: 336 irq_free_desc(lvq->config.irq); 337destroy_vring: 338 vring_del_virtqueue(vq); 339unmap: 340 lguest_unmap(lvq->pages); 341free_lvq: 342 kfree(lvq); 343 return ERR_PTR(err); 344} 345/*:*/ 346 347/* Cleaning up a virtqueue is easy */ 348static void lg_del_vq(struct virtqueue *vq) 349{ 350 struct lguest_vq_info *lvq = vq->priv; 351 352 /* Release the interrupt */ 353 free_irq(lvq->config.irq, vq); 354 /* Tell virtio_ring.c to free the virtqueue. */ 355 vring_del_virtqueue(vq); 356 /* Unmap the pages containing the ring. */ 357 lguest_unmap(lvq->pages); 358 /* Free our own queue information. */ 359 kfree(lvq); 360} 361 362static void lg_del_vqs(struct virtio_device *vdev) 363{ 364 struct virtqueue *vq, *n; 365 366 list_for_each_entry_safe(vq, n, &vdev->vqs, list) 367 lg_del_vq(vq); 368} 369 370static int lg_find_vqs(struct virtio_device *vdev, unsigned nvqs, 371 struct virtqueue *vqs[], 372 vq_callback_t *callbacks[], 373 const char *names[]) 374{ 375 struct lguest_device *ldev = to_lgdev(vdev); 376 int i; 377 378 /* We must have this many virtqueues. */ 379 if (nvqs > ldev->desc->num_vq) 380 return -ENOENT; 381 382 for (i = 0; i < nvqs; ++i) { 383 vqs[i] = lg_find_vq(vdev, i, callbacks[i], names[i]); 384 if (IS_ERR(vqs[i])) 385 goto error; 386 } 387 return 0; 388 389error: 390 lg_del_vqs(vdev); 391 return PTR_ERR(vqs[i]); 392} 393 394static const char *lg_bus_name(struct virtio_device *vdev) 395{ 396 return ""; 397} 398 399/* The ops structure which hooks everything together. */ 400static const struct virtio_config_ops lguest_config_ops = { 401 .get_features = lg_get_features, 402 .finalize_features = lg_finalize_features, 403 .get = lg_get, 404 .set = lg_set, 405 .get_status = lg_get_status, 406 .set_status = lg_set_status, 407 .reset = lg_reset, 408 .find_vqs = lg_find_vqs, 409 .del_vqs = lg_del_vqs, 410 .bus_name = lg_bus_name, 411}; 412 413/* 414 * The root device for the lguest virtio devices. This makes them appear as 415 * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. 416 */ 417static struct device *lguest_root; 418 419/*D:120 420 * This is the core of the lguest bus: actually adding a new device. 421 * It's a separate function because it's neater that way, and because an 422 * earlier version of the code supported hotplug and unplug. They were removed 423 * early on because they were never used. 424 * 425 * As Andrew Tridgell says, "Untested code is buggy code". 426 * 427 * It's worth reading this carefully: we start with a pointer to the new device 428 * descriptor in the "lguest_devices" page, and the offset into the device 429 * descriptor page so we can uniquely identify it if things go badly wrong. 430 */ 431static void add_lguest_device(struct lguest_device_desc *d, 432 unsigned int offset) 433{ 434 struct lguest_device *ldev; 435 436 /* Start with zeroed memory; Linux's device layer counts on it. */ 437 ldev = kzalloc(sizeof(*ldev), GFP_KERNEL); 438 if (!ldev) { 439 printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n", 440 offset, d->type); 441 return; 442 } 443 444 /* This devices' parent is the lguest/ dir. */ 445 ldev->vdev.dev.parent = lguest_root; 446 /* 447 * The device type comes straight from the descriptor. There's also a 448 * device vendor field in the virtio_device struct, which we leave as 449 * 0. 450 */ 451 ldev->vdev.id.device = d->type; 452 /* 453 * We have a simple set of routines for querying the device's 454 * configuration information and setting its status. 455 */ 456 ldev->vdev.config = &lguest_config_ops; 457 /* And we remember the device's descriptor for lguest_config_ops. */ 458 ldev->desc = d; 459 460 /* 461 * register_virtio_device() sets up the generic fields for the struct 462 * virtio_device and calls device_register(). This makes the bus 463 * infrastructure look for a matching driver. 464 */ 465 if (register_virtio_device(&ldev->vdev) != 0) { 466 printk(KERN_ERR "Failed to register lguest dev %u type %u\n", 467 offset, d->type); 468 kfree(ldev); 469 } 470} 471 472/*D:110 473 * scan_devices() simply iterates through the device page. The type 0 is 474 * reserved to mean "end of devices". 475 */ 476static void scan_devices(void) 477{ 478 unsigned int i; 479 struct lguest_device_desc *d; 480 481 /* We start at the page beginning, and skip over each entry. */ 482 for (i = 0; i < PAGE_SIZE; i += desc_size(d)) { 483 d = lguest_devices + i; 484 485 /* Once we hit a zero, stop. */ 486 if (d->type == 0) 487 break; 488 489 printk("Device at %i has size %u\n", i, desc_size(d)); 490 add_lguest_device(d, i); 491 } 492} 493 494/*D:105 495 * Fairly early in boot, lguest_devices_init() is called to set up the 496 * lguest device infrastructure. We check that we are a Guest by checking 497 * pv_info.name: there are other ways of checking, but this seems most 498 * obvious to me. 499 * 500 * So we can access the "struct lguest_device_desc"s easily, we map that memory 501 * and store the pointer in the global "lguest_devices". Then we register a 502 * root device from which all our devices will hang (this seems to be the 503 * correct sysfs incantation). 504 * 505 * Finally we call scan_devices() which adds all the devices found in the 506 * lguest_devices page. 507 */ 508static int __init lguest_devices_init(void) 509{ 510 if (strcmp(pv_info.name, "lguest") != 0) 511 return 0; 512 513 lguest_root = root_device_register("lguest"); 514 if (IS_ERR(lguest_root)) 515 panic("Could not register lguest root"); 516 517 /* Devices are in a single page above top of "normal" mem */ 518 lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1); 519 520 scan_devices(); 521 return 0; 522} 523/* We do this after core stuff, but before the drivers. */ 524postcore_initcall(lguest_devices_init); 525 526/*D:150 527 * At this point in the journey we used to now wade through the lguest 528 * devices themselves: net, block and console. Since they're all now virtio 529 * devices rather than lguest-specific, I've decided to ignore them. Mostly, 530 * they're kind of boring. But this does mean you'll never experience the 531 * thrill of reading the forbidden love scene buried deep in the block driver. 532 * 533 * "make Launcher" beckons, where we answer questions like "Where do Guests 534 * come from?", and "What do you do when someone asks for optimization?". 535 */ 536