drivers/s390/virtio/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 u64 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 int 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         /* Make sure we don't have any features > 32 bits! */
 107         BUG_ON((u32)vdev->features != vdev->features);
 108
 109         memset(out_features, 0, desc->feature_len);
 110         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
 111         for (i = 0; i < bits; i++) {
 112                 if (__virtio_test_bit(vdev, i))
 113                         out_features[i / 8] |= (1 << (i % 8));
 114         }
 115
 116         return 0;
 117 }
 118
 119 /*
 120  * Reading and writing elements in config space
 121  */
 122 static void kvm_get(struct virtio_device *vdev, unsigned int offset,
 123                    void *buf, unsigned len)
 124 {
 125         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 126
 127         BUG_ON(offset + len > desc->config_len);
 128         memcpy(buf, kvm_vq_configspace(desc) + offset, len);
 129 }
 130
 131 static void kvm_set(struct virtio_device *vdev, unsigned int offset,
 132                    const void *buf, unsigned len)
 133 {
 134         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 135
 136         BUG_ON(offset + len > desc->config_len);
 137         memcpy(kvm_vq_configspace(desc) + offset, buf, len);
 138 }
 139
 140 /*
 141  * The operations to get and set the status word just access
 142  * the status field of the device descriptor. set_status will also
 143  * make a hypercall to the host, to tell about status changes
 144  */
 145 static u8 kvm_get_status(struct virtio_device *vdev)
 146 {
 147         return to_kvmdev(vdev)->desc->status;
 148 }
 149
 150 static void kvm_set_status(struct virtio_device *vdev, u8 status)
 151 {
 152         BUG_ON(!status);
 153         to_kvmdev(vdev)->desc->status = status;
 154         kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
 155                        (unsigned long) to_kvmdev(vdev)->desc);
 156 }
 157
 158 /*
 159  * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 160  * descriptor address. The Host will zero the status and all the
 161  * features.
 162  */
 163 static void kvm_reset(struct virtio_device *vdev)
 164 {
 165         kvm_hypercall1(KVM_S390_VIRTIO_RESET,
 166                        (unsigned long) to_kvmdev(vdev)->desc);
 167 }
 168
 169 /*
 170  * When the virtio_ring code wants to notify the Host, it calls us here and we
 171  * make a hypercall.  We hand the address  of the virtqueue so the Host
 172  * knows which virtqueue we're talking about.
 173  */
 174 static bool kvm_notify(struct virtqueue *vq)
 175 {
 176         long rc;
 177         struct kvm_vqconfig *config = vq->priv;
 178
 179         rc = kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
 180         if (rc < 0)
 181                 return false;
 182         return true;
 183 }
 184
 185 /*
 186  * This routine finds the first virtqueue described in the configuration of
 187  * this device and sets it up.
 188  */
 189 static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
 190                                      unsigned index,
 191                                      void (*callback)(struct virtqueue *vq),
 192                                      const char *name)
 193 {
 194         struct kvm_device *kdev = to_kvmdev(vdev);
 195         struct kvm_vqconfig *config;
 196         struct virtqueue *vq;
 197         int err;
 198
 199         if (index >= kdev->desc->num_vq)
 200                 return ERR_PTR(-ENOENT);
 201
 202         if (!name)
 203                 return NULL;
 204
 205         config = kvm_vq_config(kdev->desc)+index;
 206
 207         err = vmem_add_mapping(config->address,
 208                                vring_size(config->num,
 209                                           KVM_S390_VIRTIO_RING_ALIGN));
 210         if (err)
 211                 goto out;
 212
 213         vq = vring_new_virtqueue(index, config->num, KVM_S390_VIRTIO_RING_ALIGN,
 214                                  vdev, true, (void *) config->address,
 215                                  kvm_notify, callback, name);
 216         if (!vq) {
 217                 err = -ENOMEM;
 218                 goto unmap;
 219         }
 220
 221         /*
 222          * register a callback token
 223          * The host will sent this via the external interrupt parameter
 224          */
 225         config->token = (u64) vq;
 226
 227         vq->priv = config;
 228         return vq;
 229 unmap:
 230         vmem_remove_mapping(config->address,
 231                             vring_size(config->num,
 232                                        KVM_S390_VIRTIO_RING_ALIGN));
 233 out:
 234         return ERR_PTR(err);
 235 }
 236
 237 static void kvm_del_vq(struct virtqueue *vq)
 238 {
 239         struct kvm_vqconfig *config = vq->priv;
 240
 241         vring_del_virtqueue(vq);
 242         vmem_remove_mapping(config->address,
 243                             vring_size(config->num,
 244                                        KVM_S390_VIRTIO_RING_ALIGN));
 245 }
 246
 247 static void kvm_del_vqs(struct virtio_device *vdev)
 248 {
 249         struct virtqueue *vq, *n;
 250
 251         list_for_each_entry_safe(vq, n, &vdev->vqs, list)
 252                 kvm_del_vq(vq);
 253 }
 254
 255 static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 256                         struct virtqueue *vqs[],
 257                         vq_callback_t *callbacks[],
 258                         const char * const names[])
 259 {
 260         struct kvm_device *kdev = to_kvmdev(vdev);
 261         int i;
 262
 263         /* We must have this many virtqueues. */
 264         if (nvqs > kdev->desc->num_vq)
 265                 return -ENOENT;
 266
 267         for (i = 0; i < nvqs; ++i) {
 268                 vqs[i] = kvm_find_vq(vdev, i, callbacks[i], names[i]);
 269                 if (IS_ERR(vqs[i]))
 270                         goto error;
 271         }
 272         return 0;
 273
 274 error:
 275         kvm_del_vqs(vdev);
 276         return PTR_ERR(vqs[i]);
 277 }
 278
 279 static const char *kvm_bus_name(struct virtio_device *vdev)
 280 {
 281         return "";
 282 }
 283
 284 /*
 285  * The config ops structure as defined by virtio config
 286  */
 287 static const struct virtio_config_ops kvm_vq_configspace_ops = {
 288         .get_features = kvm_get_features,
 289         .finalize_features = kvm_finalize_features,
 290         .get = kvm_get,
 291         .set = kvm_set,
 292         .get_status = kvm_get_status,
 293         .set_status = kvm_set_status,
 294         .reset = kvm_reset,
 295         .find_vqs = kvm_find_vqs,
 296         .del_vqs = kvm_del_vqs,
 297         .bus_name = kvm_bus_name,
 298 };
 299
 300 /*
 301  * The root device for the kvm virtio devices.
 302  * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 303  */
 304 static struct device *kvm_root;
 305
 306 /*
 307  * adds a new device and register it with virtio
 308  * appropriate drivers are loaded by the device model
 309  */
 310 static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
 311 {
 312         struct kvm_device *kdev;
 313
 314         kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
 315         if (!kdev) {
 316                 printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
 317                        offset, d->type);
 318                 return;
 319         }
 320
 321         kdev->vdev.dev.parent = kvm_root;
 322         kdev->vdev.id.device = d->type;
 323         kdev->vdev.config = &kvm_vq_configspace_ops;
 324         kdev->desc = d;
 325
 326         if (register_virtio_device(&kdev->vdev) != 0) {
 327                 printk(KERN_ERR "Failed to register kvm device %u type %u\n",
 328                        offset, d->type);
 329                 kfree(kdev);
 330         }
 331 }
 332
 333 /*
 334  * scan_devices() simply iterates through the device page.
 335  * The type 0 is reserved to mean "end of devices".
 336  */
 337 static void scan_devices(void)
 338 {
 339         unsigned int i;
 340         struct kvm_device_desc *d;
 341
 342         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 343                 d = kvm_devices + i;
 344
 345                 if (d->type == 0)
 346                         break;
 347
 348                 add_kvm_device(d, i);
 349         }
 350 }
 351
 352 /*
 353  * match for a kvm device with a specific desc pointer
 354  */
 355 static int match_desc(struct device *dev, void *data)
 356 {
 357         struct virtio_device *vdev = dev_to_virtio(dev);
 358         struct kvm_device *kdev = to_kvmdev(vdev);
 359
 360         return kdev->desc == data;
 361 }
 362
 363 /*
 364  * hotplug_device tries to find changes in the device page.
 365  */
 366 static void hotplug_devices(struct work_struct *dummy)
 367 {
 368         unsigned int i;
 369         struct kvm_device_desc *d;
 370         struct device *dev;
 371
 372         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 373                 d = kvm_devices + i;
 374
 375                 /* end of list */
 376                 if (d->type == 0)
 377                         break;
 378
 379                 /* device already exists */
 380                 dev = device_find_child(kvm_root, d, match_desc);
 381                 if (dev) {
 382                         /* XXX check for hotplug remove */
 383                         put_device(dev);
 384                         continue;
 385                 }
 386
 387                 /* new device */
 388                 printk(KERN_INFO "Adding new virtio device %p\n", d);
 389                 add_kvm_device(d, i);
 390         }
 391 }
 392
 393 /*
 394  * we emulate the request_irq behaviour on top of s390 extints
 395  */
 396 static void kvm_extint_handler(struct ext_code ext_code,
 397                                unsigned int param32, unsigned long param64)
 398 {
 399         struct virtqueue *vq;
 400         u32 param;
 401
 402         if ((ext_code.subcode & 0xff00) != VIRTIO_SUBCODE_64)
 403                 return;
 404         inc_irq_stat(IRQEXT_VRT);
 405
 406         /* The LSB might be overloaded, we have to mask it */
 407         vq = (struct virtqueue *)(param64 & ~1UL);
 408
 409         /* We use ext_params to decide what this interrupt means */
 410         param = param32 & VIRTIO_PARAM_MASK;
 411
 412         switch (param) {
 413         case VIRTIO_PARAM_CONFIG_CHANGED:
 414                 virtio_config_changed(vq->vdev);
 415                 break;
 416         case VIRTIO_PARAM_DEV_ADD:
 417                 schedule_work(&hotplug_work);
 418                 break;
 419         case VIRTIO_PARAM_VRING_INTERRUPT:
 420         default:
 421                 vring_interrupt(0, vq);
 422                 break;
 423         }
 424 }
 425
 426 /*
 427  * For s390-virtio, we expect a page above main storage containing
 428  * the virtio configuration. Try to actually load from this area
 429  * in order to figure out if the host provides this page.
 430  */
 431 static int __init test_devices_support(unsigned long addr)
 432 {
 433         int ret = -EIO;
 434
 435         asm volatile(
 436                 "0:     lura    0,%1\n"
 437                 "1:     xgr     %0,%0\n"
 438                 "2:\n"
 439                 EX_TABLE(0b,2b)
 440                 EX_TABLE(1b,2b)
 441                 : "+d" (ret)
 442                 : "a" (addr)
 443                 : "0", "cc");
 444         return ret;
 445 }
 446 /*
 447  * Init function for virtio
 448  * devices are in a single page above top of "normal" + standby mem
 449  */
 450 static int __init kvm_devices_init(void)
 451 {
 452         int rc;
 453         unsigned long total_memory_size = sclp.rzm * sclp.rnmax;
 454
 455         if (!MACHINE_IS_KVM)
 456                 return -ENODEV;
 457
 458         if (test_devices_support(total_memory_size) < 0)
 459                 return -ENODEV;
 460
 461         pr_warn("The s390-virtio transport is deprecated. Please switch to a modern host providing virtio-ccw.\n");
 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_irq(EXT_IRQ_CP_SERVICE, kvm_extint_handler);
 481
 482         scan_devices();
 483         return 0;
 484 }
 485
 486 /* code for early console output with virtio_console */
 487 static 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);