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/interrupt.h>
  19 #include <linux/virtio_ring.h>
  20 #include <linux/pfn.h>
  21 #include <asm/io.h>
  22 #include <asm/kvm_para.h>
  23 #include <asm/kvm_virtio.h>
  24 #include <asm/setup.h>
  25 #include <asm/s390_ext.h>
  26
  27 #define VIRTIO_SUBCODE_64 0x0D00
  28
  29 /*
  30  * The pointer to our (page) of device descriptions.
  31  */
  32 static void *kvm_devices;
  33
  34 struct kvm_device {
  35         struct virtio_device vdev;
  36         struct kvm_device_desc *desc;
  37 };
  38
  39 #define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)
  40
  41 /*
  42  * memory layout:
  43  * - kvm_device_descriptor
  44  *        struct kvm_device_desc
  45  * - configuration
  46  *        struct kvm_vqconfig
  47  * - feature bits
  48  * - config space
  49  */
  50 static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
  51 {
  52         return (struct kvm_vqconfig *)(desc + 1);
  53 }
  54
  55 static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
  56 {
  57         return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
  58 }
  59
  60 static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
  61 {
  62         return kvm_vq_features(desc) + desc->feature_len * 2;
  63 }
  64
  65 /*
  66  * The total size of the config page used by this device (incl. desc)
  67  */
  68 static unsigned desc_size(const struct kvm_device_desc *desc)
  69 {
  70         return sizeof(*desc)
  71                 + desc->num_vq * sizeof(struct kvm_vqconfig)
  72                 + desc->feature_len * 2
  73                 + desc->config_len;
  74 }
  75
  76 /* This gets the device's feature bits. */
  77 static u32 kvm_get_features(struct virtio_device *vdev)
  78 {
  79         unsigned int i;
  80         u32 features = 0;
  81         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  82         u8 *in_features = kvm_vq_features(desc);
  83
  84         for (i = 0; i < min(desc->feature_len * 8, 32); i++)
  85                 if (in_features[i / 8] & (1 << (i % 8)))
  86                         features |= (1 << i);
  87         return features;
  88 }
  89
  90 static void kvm_set_features(struct virtio_device *vdev, u32 features)
  91 {
  92         unsigned int i;
  93         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
  94         /* Second half of bitmap is features we accept. */
  95         u8 *out_features = kvm_vq_features(desc) + desc->feature_len;
  96
  97         memset(out_features, 0, desc->feature_len);
  98         for (i = 0; i < min(desc->feature_len * 8, 32); i++) {
  99                 if (features & (1 << i))
 100                         out_features[i / 8] |= (1 << (i % 8));
 101         }
 102 }
 103
 104 /*
 105  * Reading and writing elements in config space
 106  */
 107 static void kvm_get(struct virtio_device *vdev, unsigned int offset,
 108                    void *buf, unsigned len)
 109 {
 110         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 111
 112         BUG_ON(offset + len > desc->config_len);
 113         memcpy(buf, kvm_vq_configspace(desc) + offset, len);
 114 }
 115
 116 static void kvm_set(struct virtio_device *vdev, unsigned int offset,
 117                    const void *buf, unsigned len)
 118 {
 119         struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
 120
 121         BUG_ON(offset + len > desc->config_len);
 122         memcpy(kvm_vq_configspace(desc) + offset, buf, len);
 123 }
 124
 125 /*
 126  * The operations to get and set the status word just access
 127  * the status field of the device descriptor. set_status will also
 128  * make a hypercall to the host, to tell about status changes
 129  */
 130 static u8 kvm_get_status(struct virtio_device *vdev)
 131 {
 132         return to_kvmdev(vdev)->desc->status;
 133 }
 134
 135 static void kvm_set_status(struct virtio_device *vdev, u8 status)
 136 {
 137         BUG_ON(!status);
 138         to_kvmdev(vdev)->desc->status = status;
 139         kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
 140                        (unsigned long) to_kvmdev(vdev)->desc);
 141 }
 142
 143 /*
 144  * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 145  * descriptor address. The Host will zero the status and all the
 146  * features.
 147  */
 148 static void kvm_reset(struct virtio_device *vdev)
 149 {
 150         kvm_hypercall1(KVM_S390_VIRTIO_RESET,
 151                        (unsigned long) to_kvmdev(vdev)->desc);
 152 }
 153
 154 /*
 155  * When the virtio_ring code wants to notify the Host, it calls us here and we
 156  * make a hypercall.  We hand the address  of the virtqueue so the Host
 157  * knows which virtqueue we're talking about.
 158  */
 159 static void kvm_notify(struct virtqueue *vq)
 160 {
 161         struct kvm_vqconfig *config = vq->priv;
 162
 163         kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
 164 }
 165
 166 /*
 167  * This routine finds the first virtqueue described in the configuration of
 168  * this device and sets it up.
 169  */
 170 static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
 171                                     unsigned index,
 172                                     void (*callback)(struct virtqueue *vq))
 173 {
 174         struct kvm_device *kdev = to_kvmdev(vdev);
 175         struct kvm_vqconfig *config;
 176         struct virtqueue *vq;
 177         int err;
 178
 179         if (index >= kdev->desc->num_vq)
 180                 return ERR_PTR(-ENOENT);
 181
 182         config = kvm_vq_config(kdev->desc)+index;
 183
 184         err = vmem_add_mapping(config->address,
 185                                vring_size(config->num, PAGE_SIZE));
 186         if (err)
 187                 goto out;
 188
 189         vq = vring_new_virtqueue(config->num, vdev, (void *) config->address,
 190                                  kvm_notify, callback);
 191         if (!vq) {
 192                 err = -ENOMEM;
 193                 goto unmap;
 194         }
 195
 196         /*
 197          * register a callback token
 198          * The host will sent this via the external interrupt parameter
 199          */
 200         config->token = (u64) vq;
 201
 202         vq->priv = config;
 203         return vq;
 204 unmap:
 205         vmem_remove_mapping(config->address,
 206                             vring_size(config->num, PAGE_SIZE));
 207 out:
 208         return ERR_PTR(err);
 209 }
 210
 211 static void kvm_del_vq(struct virtqueue *vq)
 212 {
 213         struct kvm_vqconfig *config = vq->priv;
 214
 215         vring_del_virtqueue(vq);
 216         vmem_remove_mapping(config->address,
 217                             vring_size(config->num, PAGE_SIZE));
 218 }
 219
 220 /*
 221  * The config ops structure as defined by virtio config
 222  */
 223 static struct virtio_config_ops kvm_vq_configspace_ops = {
 224         .get_features = kvm_get_features,
 225         .set_features = kvm_set_features,
 226         .get = kvm_get,
 227         .set = kvm_set,
 228         .get_status = kvm_get_status,
 229         .set_status = kvm_set_status,
 230         .reset = kvm_reset,
 231         .find_vq = kvm_find_vq,
 232         .del_vq = kvm_del_vq,
 233 };
 234
 235 /*
 236  * The root device for the kvm virtio devices.
 237  * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 238  */
 239 static struct device kvm_root = {
 240         .parent = NULL,
 241         .bus_id = "kvm_s390",
 242 };
 243
 244 /*
 245  * adds a new device and register it with virtio
 246  * appropriate drivers are loaded by the device model
 247  */
 248 static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
 249 {
 250         struct kvm_device *kdev;
 251
 252         kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
 253         if (!kdev) {
 254                 printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
 255                        offset, d->type);
 256                 return;
 257         }
 258
 259         kdev->vdev.dev.parent = &kvm_root;
 260         kdev->vdev.id.device = d->type;
 261         kdev->vdev.config = &kvm_vq_configspace_ops;
 262         kdev->desc = d;
 263
 264         if (register_virtio_device(&kdev->vdev) != 0) {
 265                 printk(KERN_ERR "Failed to register kvm device %u type %u\n",
 266                        offset, d->type);
 267                 kfree(kdev);
 268         }
 269 }
 270
 271 /*
 272  * scan_devices() simply iterates through the device page.
 273  * The type 0 is reserved to mean "end of devices".
 274  */
 275 static void scan_devices(void)
 276 {
 277         unsigned int i;
 278         struct kvm_device_desc *d;
 279
 280         for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
 281                 d = kvm_devices + i;
 282
 283                 if (d->type == 0)
 284                         break;
 285
 286                 add_kvm_device(d, i);
 287         }
 288 }
 289
 290 /*
 291  * we emulate the request_irq behaviour on top of s390 extints
 292  */
 293 static void kvm_extint_handler(u16 code)
 294 {
 295         void *data = (void *) *(long *) __LC_PFAULT_INTPARM;
 296         u16 subcode = S390_lowcore.cpu_addr;
 297
 298         if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
 299                 return;
 300
 301         vring_interrupt(0, data);
 302 }
 303
 304 /*
 305  * Init function for virtio
 306  * devices are in a single page above top of "normal" mem
 307  */
 308 static int __init kvm_devices_init(void)
 309 {
 310         int rc;
 311
 312         if (!MACHINE_IS_KVM)
 313                 return -ENODEV;
 314
 315         rc = device_register(&kvm_root);
 316         if (rc) {
 317                 printk(KERN_ERR "Could not register kvm_s390 root device");
 318                 return rc;
 319         }
 320
 321         rc = vmem_add_mapping(PFN_PHYS(max_pfn), PAGE_SIZE);
 322         if (rc) {
 323                 device_unregister(&kvm_root);
 324                 return rc;
 325         }
 326
 327         kvm_devices = (void *) PFN_PHYS(max_pfn);
 328
 329         ctl_set_bit(0, 9);
 330         register_external_interrupt(0x2603, kvm_extint_handler);
 331
 332         scan_devices();
 333         return 0;
 334 }
 335
 336 /*
 337  * We do this after core stuff, but before the drivers.
 338  */
 339 postcore_initcall(kvm_devices_init);