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 #include <asm/s390_rdev.h>
  28
  29 #define VIRTIO_SUBCODE_64 0x0D00
  30
  31 /*
  32  * The pointer to our (page) of device descriptions.
  33  */
  34 static void *kvm_devices;
  35
  36 struct kvm_device {
  37         struct virtio_device vdev;
  38         struct kvm_device_desc *desc;
  39 };
  40
  41 #define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)
  42
  43 /*
  44  * memory layout:
  45  * - kvm_device_descriptor
  46  *        struct kvm_device_desc
  47  * - configuration
  48  *        struct kvm_vqconfig
  49  * - feature bits
  50  * - config space
  51  */
  52 static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
  53 {
  54         return (struct kvm_vqconfig *)(desc + 1);
  55 }
  56
  57 static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
  58 {
  59         return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
  60 }
  61
  62 static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
  63 {
  64         return kvm_vq_features(desc) + desc->feature_len * 2;
  65 }
  66
  67 /*
  68  * The total size of the config page used by this device (incl. desc)
  69  */
  70 static unsigned desc_size(const struct kvm_device_desc *desc)
  71 {
  72         return sizeof(*desc)
  73                 + desc->num_vq * sizeof(struct kvm_vqconfig)
  74                 + desc->feature_len * 2
  75                 + desc->config_len;
  76 }
  77
  78 /* This gets the device's feature bits. */
  79 static u32 kvm_get_features(struct virtio_device *vdev)
  80 {
  81         unsigned int i;
  82         u32 features = 0;
  83         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  84         u8 *in_features = kvm_vq_features(desc);
  85
  86         for (i = 0; i < min(desc->feature_len * 8, 32); i++)
  87                 if (in_features[i / 8] & (1 << (i % 8)))
  88                         features |= (1 << i);
  89         return features;
  90 }
  91
  92 static void kvm_finalize_features(struct virtio_device *vdev)
  93 {
  94         unsigned int i, bits;
  95         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  96         /* Second half of bitmap is features we accept. */
  97         u8 *out_features = kvm_vq_features(desc) + desc->feature_len;
  98
  99         /* Give virtio_ring a chance to accept features. */
 100         vring_transport_features(vdev);
 101
 102         memset(out_features, 0, desc->feature_len);
 103         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
 104         for (i = 0; i < bits; i++) {
 105                 if (test_bit(i, vdev->features))
 106                         out_features[i / 8] |= (1 << (i % 8));
 107         }
 108 }
 109
 110 /*
 111  * Reading and writing elements in config space
 112  */
 113 static void kvm_get(struct virtio_device *vdev, unsigned int offset,
 114                    void *buf, unsigned len)
 115 {
 116         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 117
 118         BUG_ON(offset + len > desc->config_len);
 119         memcpy(buf, kvm_vq_configspace(desc) + offset, len);
 120 }
 121
 122 static void kvm_set(struct virtio_device *vdev, unsigned int offset,
 123                    const 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(kvm_vq_configspace(desc) + offset, buf, len);
 129 }
 130
 131 /*
 132  * The operations to get and set the status word just access
 133  * the status field of the device descriptor. set_status will also
 134  * make a hypercall to the host, to tell about status changes
 135  */
 136 static u8 kvm_get_status(struct virtio_device *vdev)
 137 {
 138         return to_kvmdev(vdev)->desc->status;
 139 }
 140
 141 static void kvm_set_status(struct virtio_device *vdev, u8 status)
 142 {
 143         BUG_ON(!status);
 144         to_kvmdev(vdev)->desc->status = status;
 145         kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
 146                        (unsigned long) to_kvmdev(vdev)->desc);
 147 }
 148
 149 /*
 150  * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 151  * descriptor address. The Host will zero the status and all the
 152  * features.
 153  */
 154 static void kvm_reset(struct virtio_device *vdev)
 155 {
 156         kvm_hypercall1(KVM_S390_VIRTIO_RESET,
 157                        (unsigned long) to_kvmdev(vdev)->desc);
 158 }
 159
 160 /*
 161  * When the virtio_ring code wants to notify the Host, it calls us here and we
 162  * make a hypercall.  We hand the address  of the virtqueue so the Host
 163  * knows which virtqueue we're talking about.
 164  */
 165 static void kvm_notify(struct virtqueue *vq)
 166 {
 167         struct kvm_vqconfig *config = vq->priv;
 168
 169         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
 170 }
 171
 172 /*
 173  * This routine finds the first virtqueue described in the configuration of
 174  * this device and sets it up.
 175  */
 176 static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
 177                                     unsigned index,
 178                                     void (*callback)(struct virtqueue *vq))
 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, PAGE_SIZE));
 192         if (err)
 193                 goto out;
 194
 195         vq = vring_new_virtqueue(config->num, vdev, (void *) config->address,
 196                                  kvm_notify, callback);
 197         if (!vq) {
 198                 err = -ENOMEM;
 199                 goto unmap;
 200         }
 201
 202         /*
 203          * register a callback token
 204          * The host will sent this via the external interrupt parameter
 205          */
 206         config->token = (u64) vq;
 207
 208         vq->priv = config;
 209         return vq;
 210 unmap:
 211         vmem_remove_mapping(config->address,
 212                             vring_size(config->num, PAGE_SIZE));
 213 out:
 214         return ERR_PTR(err);
 215 }
 216
 217 static void kvm_del_vq(struct virtqueue *vq)
 218 {
 219         struct kvm_vqconfig *config = vq->priv;
 220
 221         vring_del_virtqueue(vq);
 222         vmem_remove_mapping(config->address,
 223                             vring_size(config->num, PAGE_SIZE));
 224 }
 225
 226 /*
 227  * The config ops structure as defined by virtio config
 228  */
 229 static struct virtio_config_ops kvm_vq_configspace_ops = {
 230         .get_features = kvm_get_features,
 231         .finalize_features = kvm_finalize_features,
 232         .get = kvm_get,
 233         .set = kvm_set,
 234         .get_status = kvm_get_status,
 235         .set_status = kvm_set_status,
 236         .reset = kvm_reset,
 237         .find_vq = kvm_find_vq,
 238         .del_vq = kvm_del_vq,
 239 };
 240
 241 /*
 242  * The root device for the kvm virtio devices.
 243  * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 244  */
 245 static struct device *kvm_root;
 246
 247 /*
 248  * adds a new device and register it with virtio
 249  * appropriate drivers are loaded by the device model
 250  */
 251 static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
 252 {
 253         struct kvm_device *kdev;
 254
 255         kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
 256         if (!kdev) {
 257                 printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
 258                        offset, d->type);
 259                 return;
 260         }
 261
 262         kdev->vdev.dev.parent = kvm_root;
 263         kdev->vdev.id.device = d->type;
 264         kdev->vdev.config = &kvm_vq_configspace_ops;
 265         kdev->desc = d;
 266
 267         if (register_virtio_device(&kdev->vdev) != 0) {
 268                 printk(KERN_ERR "Failed to register kvm device %u type %u\n",
 269                        offset, d->type);
 270                 kfree(kdev);
 271         }
 272 }
 273
 274 /*
 275  * scan_devices() simply iterates through the device page.
 276  * The type 0 is reserved to mean "end of devices".
 277  */
 278 static void scan_devices(void)
 279 {
 280         unsigned int i;
 281         struct kvm_device_desc *d;
 282
 283         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 284                 d = kvm_devices + i;
 285
 286                 if (d->type == 0)
 287                         break;
 288
 289                 add_kvm_device(d, i);
 290         }
 291 }
 292
 293 /*
 294  * we emulate the request_irq behaviour on top of s390 extints
 295  */
 296 static void kvm_extint_handler(u16 code)
 297 {
 298         void *data = (void *) *(long *) __LC_PFAULT_INTPARM;
 299         u16 subcode = S390_lowcore.cpu_addr;
 300
 301         if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
 302                 return;
 303
 304         vring_interrupt(0, data);
 305 }
 306
 307 /*
 308  * Init function for virtio
 309  * devices are in a single page above top of "normal" mem
 310  */
 311 static int __init kvm_devices_init(void)
 312 {
 313         int rc;
 314
 315         if (!MACHINE_IS_KVM)
 316                 return -ENODEV;
 317
 318         kvm_root = s390_root_dev_register("kvm_s390");
 319         if (IS_ERR(kvm_root)) {
 320                 rc = PTR_ERR(kvm_root);
 321                 printk(KERN_ERR "Could not register kvm_s390 root device");
 322                 return rc;
 323         }
 324
 325         rc = vmem_add_mapping(PFN_PHYS(max_pfn), PAGE_SIZE);
 326         if (rc) {
 327                 s390_root_dev_unregister(kvm_root);
 328                 return rc;
 329         }
 330
 331         kvm_devices = (void *) PFN_PHYS(max_pfn);
 332
 333         ctl_set_bit(0, 9);
 334         register_external_interrupt(0x2603, kvm_extint_handler);
 335
 336         scan_devices();
 337         return 0;
 338 }
 339
 340 /* code for early console output with virtio_console */
 341 static __init int early_put_chars(u32 vtermno, const char *buf, int count)
 342 {
 343         char scratch[17];
 344         unsigned int len = count;
 345
 346         if (len > sizeof(scratch) - 1)
 347                 len = sizeof(scratch) - 1;
 348         scratch[len] = '\0';
 349         memcpy(scratch, buf, len);
 350         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, __pa(scratch));
 351         return len;
 352 }
 353
 354 void __init s390_virtio_console_init(void)
 355 {
 356         virtio_cons_early_init(early_put_chars);
 357 }
 358
 359 /*
 360  * We do this after core stuff, but before the drivers.
 361  */
 362 postcore_initcall(kvm_devices_init);