drivers/s390/kvm/kvm_virtio.c

   1 /*
   2  * kvm_virtio.c - 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/init.h>
  14 #include <linux/bootmem.h>
  15 #include <linux/err.h>
  16 #include <linux/virtio.h>
  17 #include <linux/virtio_config.h>
  18 #include <linux/virtio_console.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/virtio_ring.h>
  21 #include <linux/pfn.h>
  22 #include <asm/io.h>
  23 #include <asm/kvm_para.h>
  24 #include <asm/kvm_virtio.h>
  25 #include <asm/setup.h>
  26 #include <asm/s390_ext.h>
  27
  28 #define VIRTIO_SUBCODE_64 0x0D00
  29
  30 /*
  31  * The pointer to our (page) of device descriptions.
  32  */
  33 static void *kvm_devices;
  34
  35 struct kvm_device {
  36         struct virtio_device vdev;
  37         struct kvm_device_desc *desc;
  38 };
  39
  40 #define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)
  41
  42 /*
  43  * memory layout:
  44  * - kvm_device_descriptor
  45  *        struct kvm_device_desc
  46  * - configuration
  47  *        struct kvm_vqconfig
  48  * - feature bits
  49  * - config space
  50  */
  51 static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
  52 {
  53         return (struct kvm_vqconfig *)(desc + 1);
  54 }
  55
  56 static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
  57 {
  58         return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
  59 }
  60
  61 static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
  62 {
  63         return kvm_vq_features(desc) + desc->feature_len * 2;
  64 }
  65
  66 /*
  67  * The total size of the config page used by this device (incl. desc)
  68  */
  69 static unsigned desc_size(const struct kvm_device_desc *desc)
  70 {
  71         return sizeof(*desc)
  72                 + desc->num_vq * sizeof(struct kvm_vqconfig)
  73                 + desc->feature_len * 2
  74                 + desc->config_len;
  75 }
  76
  77 /* This gets the device's feature bits. */
  78 static u32 kvm_get_features(struct virtio_device *vdev)
  79 {
  80         unsigned int i;
  81         u32 features = 0;
  82         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  83         u8 *in_features = kvm_vq_features(desc);
  84
  85         for (i = 0; i < min(desc->feature_len * 8, 32); i++)
  86                 if (in_features[i / 8] & (1 << (i % 8)))
  87                         features |= (1 << i);
  88         return features;
  89 }
  90
  91 static void kvm_finalize_features(struct virtio_device *vdev)
  92 {
  93         unsigned int i, bits;
  94         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  95         /* Second half of bitmap is features we accept. */
  96         u8 *out_features = kvm_vq_features(desc) + desc->feature_len;
  97
  98         /* Give virtio_ring a chance to accept features. */
  99         vring_transport_features(vdev);
 100
 101         memset(out_features, 0, desc->feature_len);
 102         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
 103         for (i = 0; i < bits; i++) {
 104                 if (test_bit(i, vdev->features))
 105                         out_features[i / 8] |= (1 << (i % 8));
 106         }
 107 }
 108
 109 /*
 110  * Reading and writing elements in config space
 111  */
 112 static void kvm_get(struct virtio_device *vdev, unsigned int offset,
 113                    void *buf, unsigned len)
 114 {
 115         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 116
 117         BUG_ON(offset + len > desc->config_len);
 118         memcpy(buf, kvm_vq_configspace(desc) + offset, len);
 119 }
 120
 121 static void kvm_set(struct virtio_device *vdev, unsigned int offset,
 122                    const void *buf, unsigned len)
 123 {
 124         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 125
 126         BUG_ON(offset + len > desc->config_len);
 127         memcpy(kvm_vq_configspace(desc) + offset, buf, len);
 128 }
 129
 130 /*
 131  * The operations to get and set the status word just access
 132  * the status field of the device descriptor. set_status will also
 133  * make a hypercall to the host, to tell about status changes
 134  */
 135 static u8 kvm_get_status(struct virtio_device *vdev)
 136 {
 137         return to_kvmdev(vdev)->desc->status;
 138 }
 139
 140 static void kvm_set_status(struct virtio_device *vdev, u8 status)
 141 {
 142         BUG_ON(!status);
 143         to_kvmdev(vdev)->desc->status = status;
 144         kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
 145                        (unsigned long) to_kvmdev(vdev)->desc);
 146 }
 147
 148 /*
 149  * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 150  * descriptor address. The Host will zero the status and all the
 151  * features.
 152  */
 153 static void kvm_reset(struct virtio_device *vdev)
 154 {
 155         kvm_hypercall1(KVM_S390_VIRTIO_RESET,
 156                        (unsigned long) to_kvmdev(vdev)->desc);
 157 }
 158
 159 /*
 160  * When the virtio_ring code wants to notify the Host, it calls us here and we
 161  * make a hypercall.  We hand the address  of the virtqueue so the Host
 162  * knows which virtqueue we're talking about.
 163  */
 164 static void kvm_notify(struct virtqueue *vq)
 165 {
 166         struct kvm_vqconfig *config = vq->priv;
 167
 168         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
 169 }
 170
 171 /*
 172  * This routine finds the first virtqueue described in the configuration of
 173  * this device and sets it up.
 174  */
 175 static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
 176                                      unsigned index,
 177                                      void (*callback)(struct virtqueue *vq),
 178                                      const char *name)
 179 {
 180         struct kvm_device *kdev = to_kvmdev(vdev);
 181         struct kvm_vqconfig *config;
 182         struct virtqueue *vq;
 183         int err;
 184
 185         if (index >= kdev->desc->num_vq)
 186                 return ERR_PTR(-ENOENT);
 187
 188         config = kvm_vq_config(kdev->desc)+index;
 189
 190         err = vmem_add_mapping(config->address,
 191                                vring_size(config->num,
 192                                           KVM_S390_VIRTIO_RING_ALIGN));
 193         if (err)
 194                 goto out;
 195
 196         vq = vring_new_virtqueue(config->num, KVM_S390_VIRTIO_RING_ALIGN,
 197                                  vdev, (void *) config->address,
 198                                  kvm_notify, callback, name);
 199         if (!vq) {
 200                 err = -ENOMEM;
 201                 goto unmap;
 202         }
 203
 204         /*
 205          * register a callback token
 206          * The host will sent this via the external interrupt parameter
 207          */
 208         config->token = (u64) vq;
 209
 210         vq->priv = config;
 211         return vq;
 212 unmap:
 213         vmem_remove_mapping(config->address,
 214                             vring_size(config->num,
 215                                        KVM_S390_VIRTIO_RING_ALIGN));
 216 out:
 217         return ERR_PTR(err);
 218 }
 219
 220 static void kvm_del_vq(struct virtqueue *vq)
 221 {
 222         struct kvm_vqconfig *config = vq->priv;
 223
 224         vring_del_virtqueue(vq);
 225         vmem_remove_mapping(config->address,
 226                             vring_size(config->num,
 227                                        KVM_S390_VIRTIO_RING_ALIGN));
 228 }
 229
 230 static void kvm_del_vqs(struct virtio_device *vdev)
 231 {
 232         struct virtqueue *vq, *n;
 233
 234         list_for_each_entry_safe(vq, n, &vdev->vqs, list)
 235                 kvm_del_vq(vq);
 236 }
 237
 238 static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 239                         struct virtqueue *vqs[],
 240                         vq_callback_t *callbacks[],
 241                         const char *names[])
 242 {
 243         struct kvm_device *kdev = to_kvmdev(vdev);
 244         int i;
 245
 246         /* We must have this many virtqueues. */
 247         if (nvqs > kdev->desc->num_vq)
 248                 return -ENOENT;
 249
 250         for (i = 0; i < nvqs; ++i) {
 251                 vqs[i] = kvm_find_vq(vdev, i, callbacks[i], names[i]);
 252                 if (IS_ERR(vqs[i]))
 253                         goto error;
 254         }
 255         return 0;
 256
 257 error:
 258         kvm_del_vqs(vdev);
 259         return PTR_ERR(vqs[i]);
 260 }
 261
 262 /*
 263  * The config ops structure as defined by virtio config
 264  */
 265 static struct virtio_config_ops kvm_vq_configspace_ops = {
 266         .get_features = kvm_get_features,
 267         .finalize_features = kvm_finalize_features,
 268         .get = kvm_get,
 269         .set = kvm_set,
 270         .get_status = kvm_get_status,
 271         .set_status = kvm_set_status,
 272         .reset = kvm_reset,
 273         .find_vqs = kvm_find_vqs,
 274         .del_vqs = kvm_del_vqs,
 275 };
 276
 277 /*
 278  * The root device for the kvm virtio devices.
 279  * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 280  */
 281 static struct device *kvm_root;
 282
 283 /*
 284  * adds a new device and register it with virtio
 285  * appropriate drivers are loaded by the device model
 286  */
 287 static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
 288 {
 289         struct kvm_device *kdev;
 290
 291         kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
 292         if (!kdev) {
 293                 printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
 294                        offset, d->type);
 295                 return;
 296         }
 297
 298         kdev->vdev.dev.parent = kvm_root;
 299         kdev->vdev.id.device = d->type;
 300         kdev->vdev.config = &kvm_vq_configspace_ops;
 301         kdev->desc = d;
 302
 303         if (register_virtio_device(&kdev->vdev) != 0) {
 304                 printk(KERN_ERR "Failed to register kvm device %u type %u\n",
 305                        offset, d->type);
 306                 kfree(kdev);
 307         }
 308 }
 309
 310 /*
 311  * scan_devices() simply iterates through the device page.
 312  * The type 0 is reserved to mean "end of devices".
 313  */
 314 static void scan_devices(void)
 315 {
 316         unsigned int i;
 317         struct kvm_device_desc *d;
 318
 319         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 320                 d = kvm_devices + i;
 321
 322                 if (d->type == 0)
 323                         break;
 324
 325                 add_kvm_device(d, i);
 326         }
 327 }
 328
 329 /*
 330  * we emulate the request_irq behaviour on top of s390 extints
 331  */
 332 static void kvm_extint_handler(u16 code)
 333 {
 334         struct virtqueue *vq;
 335         u16 subcode;
 336         int config_changed;
 337
 338         subcode = S390_lowcore.cpu_addr;
 339         if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
 340                 return;
 341
 342         /* The LSB might be overloaded, we have to mask it */
 343         vq = (struct virtqueue *)(S390_lowcore.ext_params2 & ~1UL);
 344
 345         /* We use the LSB of extparam, to decide, if this interrupt is a config
 346          * change or a "standard" interrupt */
 347         config_changed = S390_lowcore.ext_params & 1;
 348
 349         if (config_changed) {
 350                 struct virtio_driver *drv;
 351                 drv = container_of(vq->vdev->dev.driver,
 352                                    struct virtio_driver, driver);
 353                 if (drv->config_changed)
 354                         drv->config_changed(vq->vdev);
 355         } else
 356                 vring_interrupt(0, vq);
 357 }
 358
 359 /*
 360  * Init function for virtio
 361  * devices are in a single page above top of "normal" mem
 362  */
 363 static int __init kvm_devices_init(void)
 364 {
 365         int rc;
 366
 367         if (!MACHINE_IS_KVM)
 368                 return -ENODEV;
 369
 370         kvm_root = root_device_register("kvm_s390");
 371         if (IS_ERR(kvm_root)) {
 372                 rc = PTR_ERR(kvm_root);
 373                 printk(KERN_ERR "Could not register kvm_s390 root device");
 374                 return rc;
 375         }
 376
 377         rc = vmem_add_mapping(real_memory_size, PAGE_SIZE);
 378         if (rc) {
 379                 root_device_unregister(kvm_root);
 380                 return rc;
 381         }
 382
 383         kvm_devices = (void *) real_memory_size;
 384
 385         ctl_set_bit(0, 9);
 386         register_external_interrupt(0x2603, kvm_extint_handler);
 387
 388         scan_devices();
 389         return 0;
 390 }
 391
 392 /* code for early console output with virtio_console */
 393 static __init int early_put_chars(u32 vtermno, const char *buf, int count)
 394 {
 395         char scratch[17];
 396         unsigned int len = count;
 397
 398         if (len > sizeof(scratch) - 1)
 399                 len = sizeof(scratch) - 1;
 400         scratch[len] = '\0';
 401         memcpy(scratch, buf, len);
 402         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, __pa(scratch));
 403         return len;
 404 }
 405
 406 static int __init s390_virtio_console_init(void)
 407 {
 408         if (!MACHINE_IS_KVM)
 409                 return -ENODEV;
 410         return virtio_cons_early_init(early_put_chars);
 411 }
 412 console_initcall(s390_virtio_console_init);
 413
 414
 415 /*
 416  * We do this after core stuff, but before the drivers.
 417  */
 418 postcore_initcall(kvm_devices_init);