drivers/s390/kvm/kvm_virtio.c

   1 /*
   2  * virtio for kvm on s390
   3  *
   4  * Copyright IBM Corp. 2008
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License (version 2 only)
   8  * as published by the Free Software Foundation.
   9  *
  10  *    Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
  11  */
  12
  13 #include <linux/kernel_stat.h>
  14 #include <linux/init.h>
  15 #include <linux/bootmem.h>
  16 #include <linux/err.h>
  17 #include <linux/virtio.h>
  18 #include <linux/virtio_config.h>
  19 #include <linux/slab.h>
  20 #include <linux/virtio_console.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/virtio_ring.h>
  23 #include <linux/export.h>
  24 #include <linux/pfn.h>
  25 #include <asm/io.h>
  26 #include <asm/kvm_para.h>
  27 #include <asm/kvm_virtio.h>
  28 #include <asm/sclp.h>
  29 #include <asm/setup.h>
  30 #include <asm/irq.h>
  31
  32 #define VIRTIO_SUBCODE_64 0x0D00
  33
  34 /*
  35  * The pointer to our (page) of device descriptions.
  36  */
  37 static void *kvm_devices;
  38 static struct work_struct hotplug_work;
  39
  40 struct kvm_device {
  41         struct virtio_device vdev;
  42         struct kvm_device_desc *desc;
  43 };
  44
  45 #define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)
  46
  47 /*
  48  * memory layout:
  49  * - kvm_device_descriptor
  50  *        struct kvm_device_desc
  51  * - configuration
  52  *        struct kvm_vqconfig
  53  * - feature bits
  54  * - config space
  55  */
  56 static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
  57 {
  58         return (struct kvm_vqconfig *)(desc + 1);
  59 }
  60
  61 static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
  62 {
  63         return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
  64 }
  65
  66 static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
  67 {
  68         return kvm_vq_features(desc) + desc->feature_len * 2;
  69 }
  70
  71 /*
  72  * The total size of the config page used by this device (incl. desc)
  73  */
  74 static unsigned desc_size(const struct kvm_device_desc *desc)
  75 {
  76         return sizeof(*desc)
  77                 + desc->num_vq * sizeof(struct kvm_vqconfig)
  78                 + desc->feature_len * 2
  79                 + desc->config_len;
  80 }
  81
  82 /* This gets the device's feature bits. */
  83 static u32 kvm_get_features(struct virtio_device *vdev)
  84 {
  85         unsigned int i;
  86         u32 features = 0;
  87         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  88         u8 *in_features = kvm_vq_features(desc);
  89
  90         for (i = 0; i < min(desc->feature_len * 8, 32); i++)
  91                 if (in_features[i / 8] & (1 << (i % 8)))
  92                         features |= (1 << i);
  93         return features;
  94 }
  95
  96 static void kvm_finalize_features(struct virtio_device *vdev)
  97 {
  98         unsigned int i, bits;
  99         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 100         /* Second half of bitmap is features we accept. */
 101         u8 *out_features = kvm_vq_features(desc) + desc->feature_len;
 102
 103         /* Give virtio_ring a chance to accept features. */
 104         vring_transport_features(vdev);
 105
 106         memset(out_features, 0, desc->feature_len);
 107         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
 108         for (i = 0; i < bits; i++) {
 109                 if (test_bit(i, vdev->features))
 110                         out_features[i / 8] |= (1 << (i % 8));
 111         }
 112 }
 113
 114 /*
 115  * Reading and writing elements in config space
 116  */
 117 static void kvm_get(struct virtio_device *vdev, unsigned int offset,
 118                    void *buf, unsigned len)
 119 {
 120         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 121
 122         BUG_ON(offset + len > desc->config_len);
 123         memcpy(buf, kvm_vq_configspace(desc) + offset, len);
 124 }
 125
 126 static void kvm_set(struct virtio_device *vdev, unsigned int offset,
 127                    const void *buf, unsigned len)
 128 {
 129         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 130
 131         BUG_ON(offset + len > desc->config_len);
 132         memcpy(kvm_vq_configspace(desc) + offset, buf, len);
 133 }
 134
 135 /*
 136  * The operations to get and set the status word just access
 137  * the status field of the device descriptor. set_status will also
 138  * make a hypercall to the host, to tell about status changes
 139  */
 140 static u8 kvm_get_status(struct virtio_device *vdev)
 141 {
 142         return to_kvmdev(vdev)->desc->status;
 143 }
 144
 145 static void kvm_set_status(struct virtio_device *vdev, u8 status)
 146 {
 147         BUG_ON(!status);
 148         to_kvmdev(vdev)->desc->status = status;
 149         kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
 150                        (unsigned long) to_kvmdev(vdev)->desc);
 151 }
 152
 153 /*
 154  * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 155  * descriptor address. The Host will zero the status and all the
 156  * features.
 157  */
 158 static void kvm_reset(struct virtio_device *vdev)
 159 {
 160         kvm_hypercall1(KVM_S390_VIRTIO_RESET,
 161                        (unsigned long) to_kvmdev(vdev)->desc);
 162 }
 163
 164 /*
 165  * When the virtio_ring code wants to notify the Host, it calls us here and we
 166  * make a hypercall.  We hand the address  of the virtqueue so the Host
 167  * knows which virtqueue we're talking about.
 168  */
 169 static bool kvm_notify(struct virtqueue *vq)
 170 {
 171         long rc;
 172         struct kvm_vqconfig *config = vq->priv;
 173
 174         rc = kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
 175         if (rc < 0)
 176                 return false;
 177         return true;
 178 }
 179
 180 /*
 181  * This routine finds the first virtqueue described in the configuration of
 182  * this device and sets it up.
 183  */
 184 static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
 185                                      unsigned index,
 186                                      void (*callback)(struct virtqueue *vq),
 187                                      const char *name)
 188 {
 189         struct kvm_device *kdev = to_kvmdev(vdev);
 190         struct kvm_vqconfig *config;
 191         struct virtqueue *vq;
 192         int err;
 193
 194         if (index >= kdev->desc->num_vq)
 195                 return ERR_PTR(-ENOENT);
 196
 197         if (!name)
 198                 return NULL;
 199
 200         config = kvm_vq_config(kdev->desc)+index;
 201
 202         err = vmem_add_mapping(config->address,
 203                                vring_size(config->num,
 204                                           KVM_S390_VIRTIO_RING_ALIGN));
 205         if (err)
 206                 goto out;
 207
 208         vq = vring_new_virtqueue(index, config->num, KVM_S390_VIRTIO_RING_ALIGN,
 209                                  vdev, true, (void *) config->address,
 210                                  kvm_notify, callback, name);
 211         if (!vq) {
 212                 err = -ENOMEM;
 213                 goto unmap;
 214         }
 215
 216         /*
 217          * register a callback token
 218          * The host will sent this via the external interrupt parameter
 219          */
 220         config->token = (u64) vq;
 221
 222         vq->priv = config;
 223         return vq;
 224 unmap:
 225         vmem_remove_mapping(config->address,
 226                             vring_size(config->num,
 227                                        KVM_S390_VIRTIO_RING_ALIGN));
 228 out:
 229         return ERR_PTR(err);
 230 }
 231
 232 static void kvm_del_vq(struct virtqueue *vq)
 233 {
 234         struct kvm_vqconfig *config = vq->priv;
 235
 236         vring_del_virtqueue(vq);
 237         vmem_remove_mapping(config->address,
 238                             vring_size(config->num,
 239                                        KVM_S390_VIRTIO_RING_ALIGN));
 240 }
 241
 242 static void kvm_del_vqs(struct virtio_device *vdev)
 243 {
 244         struct virtqueue *vq, *n;
 245
 246         list_for_each_entry_safe(vq, n, &vdev->vqs, list)
 247                 kvm_del_vq(vq);
 248 }
 249
 250 static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 251                         struct virtqueue *vqs[],
 252                         vq_callback_t *callbacks[],
 253                         const char *names[])
 254 {
 255         struct kvm_device *kdev = to_kvmdev(vdev);
 256         int i;
 257
 258         /* We must have this many virtqueues. */
 259         if (nvqs > kdev->desc->num_vq)
 260                 return -ENOENT;
 261
 262         for (i = 0; i < nvqs; ++i) {
 263                 vqs[i] = kvm_find_vq(vdev, i, callbacks[i], names[i]);
 264                 if (IS_ERR(vqs[i]))
 265                         goto error;
 266         }
 267         return 0;
 268
 269 error:
 270         kvm_del_vqs(vdev);
 271         return PTR_ERR(vqs[i]);
 272 }
 273
 274 static const char *kvm_bus_name(struct virtio_device *vdev)
 275 {
 276         return "";
 277 }
 278
 279 /*
 280  * The config ops structure as defined by virtio config
 281  */
 282 static const struct virtio_config_ops kvm_vq_configspace_ops = {
 283         .get_features = kvm_get_features,
 284         .finalize_features = kvm_finalize_features,
 285         .get = kvm_get,
 286         .set = kvm_set,
 287         .get_status = kvm_get_status,
 288         .set_status = kvm_set_status,
 289         .reset = kvm_reset,
 290         .find_vqs = kvm_find_vqs,
 291         .del_vqs = kvm_del_vqs,
 292         .bus_name = kvm_bus_name,
 293 };
 294
 295 /*
 296  * The root device for the kvm virtio devices.
 297  * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 298  */
 299 static struct device *kvm_root;
 300
 301 /*
 302  * adds a new device and register it with virtio
 303  * appropriate drivers are loaded by the device model
 304  */
 305 static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
 306 {
 307         struct kvm_device *kdev;
 308
 309         kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
 310         if (!kdev) {
 311                 printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
 312                        offset, d->type);
 313                 return;
 314         }
 315
 316         kdev->vdev.dev.parent = kvm_root;
 317         kdev->vdev.id.device = d->type;
 318         kdev->vdev.config = &kvm_vq_configspace_ops;
 319         kdev->desc = d;
 320
 321         if (register_virtio_device(&kdev->vdev) != 0) {
 322                 printk(KERN_ERR "Failed to register kvm device %u type %u\n",
 323                        offset, d->type);
 324                 kfree(kdev);
 325         }
 326 }
 327
 328 /*
 329  * scan_devices() simply iterates through the device page.
 330  * The type 0 is reserved to mean "end of devices".
 331  */
 332 static void scan_devices(void)
 333 {
 334         unsigned int i;
 335         struct kvm_device_desc *d;
 336
 337         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 338                 d = kvm_devices + i;
 339
 340                 if (d->type == 0)
 341                         break;
 342
 343                 add_kvm_device(d, i);
 344         }
 345 }
 346
 347 /*
 348  * match for a kvm device with a specific desc pointer
 349  */
 350 static int match_desc(struct device *dev, void *data)
 351 {
 352         struct virtio_device *vdev = dev_to_virtio(dev);
 353         struct kvm_device *kdev = to_kvmdev(vdev);
 354
 355         return kdev->desc == data;
 356 }
 357
 358 /*
 359  * hotplug_device tries to find changes in the device page.
 360  */
 361 static void hotplug_devices(struct work_struct *dummy)
 362 {
 363         unsigned int i;
 364         struct kvm_device_desc *d;
 365         struct device *dev;
 366
 367         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 368                 d = kvm_devices + i;
 369
 370                 /* end of list */
 371                 if (d->type == 0)
 372                         break;
 373
 374                 /* device already exists */
 375                 dev = device_find_child(kvm_root, d, match_desc);
 376                 if (dev) {
 377                         /* XXX check for hotplug remove */
 378                         put_device(dev);
 379                         continue;
 380                 }
 381
 382                 /* new device */
 383                 printk(KERN_INFO "Adding new virtio device %p\n", d);
 384                 add_kvm_device(d, i);
 385         }
 386 }
 387
 388 /*
 389  * we emulate the request_irq behaviour on top of s390 extints
 390  */
 391 static void kvm_extint_handler(struct ext_code ext_code,
 392                                unsigned int param32, unsigned long param64)
 393 {
 394         struct virtqueue *vq;
 395         u32 param;
 396
 397         if ((ext_code.subcode & 0xff00) != VIRTIO_SUBCODE_64)
 398                 return;
 399         inc_irq_stat(IRQEXT_VRT);
 400
 401         /* The LSB might be overloaded, we have to mask it */
 402         vq = (struct virtqueue *)(param64 & ~1UL);
 403
 404         /* We use ext_params to decide what this interrupt means */
 405         param = param32 & VIRTIO_PARAM_MASK;
 406
 407         switch (param) {
 408         case VIRTIO_PARAM_CONFIG_CHANGED:
 409         {
 410                 struct virtio_driver *drv;
 411                 drv = container_of(vq->vdev->dev.driver,
 412                                    struct virtio_driver, driver);
 413                 if (drv->config_changed)
 414                         drv->config_changed(vq->vdev);
 415
 416                 break;
 417         }
 418         case VIRTIO_PARAM_DEV_ADD:
 419                 schedule_work(&hotplug_work);
 420                 break;
 421         case VIRTIO_PARAM_VRING_INTERRUPT:
 422         default:
 423                 vring_interrupt(0, vq);
 424                 break;
 425         }
 426 }
 427
 428 /*
 429  * For s390-virtio, we expect a page above main storage containing
 430  * the virtio configuration. Try to actually load from this area
 431  * in order to figure out if the host provides this page.
 432  */
 433 static int __init test_devices_support(unsigned long addr)
 434 {
 435         int ret = -EIO;
 436
 437         asm volatile(
 438                 "0:     lura    0,%1\n"
 439                 "1:     xgr     %0,%0\n"
 440                 "2:\n"
 441                 EX_TABLE(0b,2b)
 442                 EX_TABLE(1b,2b)
 443                 : "+d" (ret)
 444                 : "a" (addr)
 445                 : "0", "cc");
 446         return ret;
 447 }
 448 /*
 449  * Init function for virtio
 450  * devices are in a single page above top of "normal" + standby mem
 451  */
 452 static int __init kvm_devices_init(void)
 453 {
 454         int rc;
 455         unsigned long total_memory_size = sclp_get_rzm() * sclp_get_rnmax();
 456
 457         if (!MACHINE_IS_KVM)
 458                 return -ENODEV;
 459
 460         if (test_devices_support(total_memory_size) < 0)
 461                 return -ENODEV;
 462
 463         rc = vmem_add_mapping(total_memory_size, PAGE_SIZE);
 464         if (rc)
 465                 return rc;
 466
 467         kvm_devices = (void *) total_memory_size;
 468
 469         kvm_root = root_device_register("kvm_s390");
 470         if (IS_ERR(kvm_root)) {
 471                 rc = PTR_ERR(kvm_root);
 472                 printk(KERN_ERR "Could not register kvm_s390 root device");
 473                 vmem_remove_mapping(total_memory_size, PAGE_SIZE);
 474                 return rc;
 475         }
 476
 477         INIT_WORK(&hotplug_work, hotplug_devices);
 478
 479         irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
 480         register_external_interrupt(0x2603, kvm_extint_handler);
 481
 482         scan_devices();
 483         return 0;
 484 }
 485
 486 /* code for early console output with virtio_console */
 487 static __init int early_put_chars(u32 vtermno, const char *buf, int count)
 488 {
 489         char scratch[17];
 490         unsigned int len = count;
 491
 492         if (len > sizeof(scratch) - 1)
 493                 len = sizeof(scratch) - 1;
 494         scratch[len] = '\0';
 495         memcpy(scratch, buf, len);
 496         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, __pa(scratch));
 497         return len;
 498 }
 499
 500 static int __init s390_virtio_console_init(void)
 501 {
 502         if (sclp_has_vt220() || sclp_has_linemode())
 503                 return -ENODEV;
 504         return virtio_cons_early_init(early_put_chars);
 505 }
 506 console_initcall(s390_virtio_console_init);
 507
 508
 509 /*
 510  * We do this after core stuff, but before the drivers.
 511  */
 512 postcore_initcall(kvm_devices_init);