kvm_virtio.c

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/*
 * virtio for kvm on s390
 *
 * Copyright IBM Corp. 2008
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (version 2 only)
 * as published by the Free Software Foundation.
 *
 *    Author(s): Christian Borntraeger <[email protected]>
 */

#include <linux/kernel_stat.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/err.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/slab.h>
#include <linux/virtio_console.h>
#include <linux/interrupt.h>
#include <linux/virtio_ring.h>
#include <linux/export.h>
#include <linux/pfn.h>
#include <asm/io.h>
#include <asm/kvm_para.h>
#include <asm/kvm_virtio.h>
#include <asm/sclp.h>
#include <asm/setup.h>
#include <asm/irq.h>

#define VIRTIO_SUBCODE_64 0x0D00

/*
 * The pointer to our (page) of device descriptions.
 */
static void *kvm_devices;
static struct work_struct hotplug_work;

struct kvm_device {
    struct virtio_device vdev;
    struct kvm_device_desc *desc;
};

#define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)

/*
 * memory layout:
 * - kvm_device_descriptor
 *        struct kvm_device_desc
 * - configuration
 *        struct kvm_vqconfig
 * - feature bits
 * - config space
 */
static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
{
    return (struct kvm_vqconfig *)(desc + 1);
}

static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
{
    return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
}

static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
{
    return kvm_vq_features(desc) + desc->feature_len * 2;
}

/*
 * The total size of the config page used by this device (incl. desc)
 */
static unsigned desc_size(const struct kvm_device_desc *desc)
{
    return sizeof(*desc)
        + desc->num_vq * sizeof(struct kvm_vqconfig)
        + desc->feature_len * 2
        + desc->config_len;
}

/* This gets the device's feature bits. */
static u32 kvm_get_features(struct virtio_device *vdev)
{
    unsigned int i;
    u32 features = 0;
    struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
    u8 *in_features = kvm_vq_features(desc);

    for (i = 0; i < min(desc->feature_len * 8, 32); i++)
        if (in_features[i / 8] & (1 << (i % 8)))
            features |= (1 << i);
    return features;
}

static void kvm_finalize_features(struct virtio_device *vdev)
{
    unsigned int i, bits;
    struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
    /* Second half of bitmap is features we accept. */
    u8 *out_features = kvm_vq_features(desc) + desc->feature_len;

    /* Give virtio_ring a chance to accept features. */
    vring_transport_features(vdev);

    memset(out_features, 0, desc->feature_len);
    bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
    for (i = 0; i < bits; i++) {
        if (test_bit(i, vdev->features))
            out_features[i / 8] |= (1 << (i % 8));
    }
}

/*
 * Reading and writing elements in config space
 */
static void kvm_get(struct virtio_device *vdev, unsigned int offset,
           void *buf, unsigned len)
{
    struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;

    BUG_ON(offset + len > desc->config_len);
    memcpy(buf, kvm_vq_configspace(desc) + offset, len);
}

static void kvm_set(struct virtio_device *vdev, unsigned int offset,
           const void *buf, unsigned len)
{
    struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;

    BUG_ON(offset + len > desc->config_len);
    memcpy(kvm_vq_configspace(desc) + offset, buf, len);
}

/*
 * The operations to get and set the status word just access
 * the status field of the device descriptor. set_status will also
 * make a hypercall to the host, to tell about status changes
 */
static u8 kvm_get_status(struct virtio_device *vdev)
{
    return to_kvmdev(vdev)->desc->status;
}

static void kvm_set_status(struct virtio_device *vdev, u8 status)
{
    BUG_ON(!status);
    to_kvmdev(vdev)->desc->status = status;
    kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
               (unsigned long) to_kvmdev(vdev)->desc);
}

/*
 * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
 * descriptor address. The Host will zero the status and all the
 * features.
 */
static void kvm_reset(struct virtio_device *vdev)
{
    kvm_hypercall1(KVM_S390_VIRTIO_RESET,
               (unsigned long) to_kvmdev(vdev)->desc);
}

/*
 * When the virtio_ring code wants to notify the Host, it calls us here and we
 * make a hypercall.  We hand the address  of the virtqueue so the Host
 * knows which virtqueue we're talking about.
 */
static void kvm_notify(struct virtqueue *vq)
{
    struct kvm_vqconfig *config = vq->priv;

    kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
}

/*
 * This routine finds the first virtqueue described in the configuration of
 * this device and sets it up.
 */
static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
                     unsigned index,
                     void (*callback)(struct virtqueue *vq),
                     const char *name)
{
    struct kvm_device *kdev = to_kvmdev(vdev);
    struct kvm_vqconfig *config;
    struct virtqueue *vq;
    int err;

    if (index >= kdev->desc->num_vq)
        return ERR_PTR(-ENOENT);

    if (!name)
        return NULL;

    config = kvm_vq_config(kdev->desc)+index;

    err = vmem_add_mapping(config->address,
                   vring_size(config->num,
                      KVM_S390_VIRTIO_RING_ALIGN));
    if (err)
        goto out;

    vq = vring_new_virtqueue(index, config->num, KVM_S390_VIRTIO_RING_ALIGN,
                 vdev, true, (void *) config->address,
                 kvm_notify, callback, name);
    if (!vq) {
        err = -ENOMEM;
        goto unmap;
    }

    /*
     * register a callback token
     * The host will sent this via the external interrupt parameter
     */
    config->token = (u64) vq;

    vq->priv = config;
    return vq;
unmap:
    vmem_remove_mapping(config->address,
                vring_size(config->num,
                       KVM_S390_VIRTIO_RING_ALIGN));
out:
    return ERR_PTR(err);
}

static void kvm_del_vq(struct virtqueue *vq)
{
    struct kvm_vqconfig *config = vq->priv;

    vring_del_virtqueue(vq);
    vmem_remove_mapping(config->address,
                vring_size(config->num,
                       KVM_S390_VIRTIO_RING_ALIGN));
}

static void kvm_del_vqs(struct virtio_device *vdev)
{
    struct virtqueue *vq, *n;

    list_for_each_entry_safe(vq, n, &vdev->vqs, list)
        kvm_del_vq(vq);
}

static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
            struct virtqueue *vqs[],
            vq_callback_t *callbacks[],
            const char *names[])
{
    struct kvm_device *kdev = to_kvmdev(vdev);
    int i;

    /* We must have this many virtqueues. */
    if (nvqs > kdev->desc->num_vq)
        return -ENOENT;

    for (i = 0; i < nvqs; ++i) {
        vqs[i] = kvm_find_vq(vdev, i, callbacks[i], names[i]);
        if (IS_ERR(vqs[i]))
            goto error;
    }
    return 0;

error:
    kvm_del_vqs(vdev);
    return PTR_ERR(vqs[i]);
}

static const char *kvm_bus_name(struct virtio_device *vdev)
{
    return "";
}

/*
 * The config ops structure as defined by virtio config
 */
static struct virtio_config_ops kvm_vq_configspace_ops = {
    .get_features = kvm_get_features,
    .finalize_features = kvm_finalize_features,
    .get = kvm_get,
    .set = kvm_set,
    .get_status = kvm_get_status,
    .set_status = kvm_set_status,
    .reset = kvm_reset,
    .find_vqs = kvm_find_vqs,
    .del_vqs = kvm_del_vqs,
    .bus_name = kvm_bus_name,
};

/*
 * The root device for the kvm virtio devices.
 * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
 */
static struct device *kvm_root;

/*
 * adds a new device and register it with virtio
 * appropriate drivers are loaded by the device model
 */
static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
{
    struct kvm_device *kdev;

    kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
    if (!kdev) {
        printk(KERN_EMERG "Cannot allocate kvm dev %u type %u\n",
               offset, d->type);
        return;
    }

    kdev->vdev.dev.parent = kvm_root;
    kdev->vdev.id.device = d->type;
    kdev->vdev.config = &kvm_vq_configspace_ops;
    kdev->desc = d;

    if (register_virtio_device(&kdev->vdev) != 0) {
        printk(KERN_ERR "Failed to register kvm device %u type %u\n",
               offset, d->type);
        kfree(kdev);
    }
}

/*
 * scan_devices() simply iterates through the device page.
 * The type 0 is reserved to mean "end of devices".
 */
static void scan_devices(void)
{
    unsigned int i;
    struct kvm_device_desc *d;

    for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
        d = kvm_devices + i;

        if (d->type == 0)
            break;

        add_kvm_device(d, i);
    }
}

/*
 * match for a kvm device with a specific desc pointer
 */
static int match_desc(struct device *dev, void *data)
{
    struct virtio_device *vdev = dev_to_virtio(dev);
    struct kvm_device *kdev = to_kvmdev(vdev);

    return kdev->desc == data;
}

/*
 * hotplug_device tries to find changes in the device page.
 */
static void hotplug_devices(struct work_struct *dummy)
{
    unsigned int i;
    struct kvm_device_desc *d;
    struct device *dev;

    for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
        d = kvm_devices + i;

        /* end of list */
        if (d->type == 0)
            break;

        /* device already exists */
        dev = device_find_child(kvm_root, d, match_desc);
        if (dev) {
            /* XXX check for hotplug remove */
            put_device(dev);
            continue;
        }

        /* new device */
        printk(KERN_INFO "Adding new virtio device %p\n", d);
        add_kvm_device(d, i);
    }
}

/*
 * we emulate the request_irq behaviour on top of s390 extints
 */
static void kvm_extint_handler(struct ext_code ext_code,
                   unsigned int param32, unsigned long param64)
{
    struct virtqueue *vq;
    u32 param;

    if ((ext_code.subcode & 0xff00) != VIRTIO_SUBCODE_64)
        return;
    kstat_cpu(smp_processor_id()).irqs[EXTINT_VRT]++;

    /* The LSB might be overloaded, we have to mask it */
    vq = (struct virtqueue *)(param64 & ~1UL);

    /* We use ext_params to decide what this interrupt means */
    param = param32 & VIRTIO_PARAM_MASK;

    switch (param) {
    case VIRTIO_PARAM_CONFIG_CHANGED:
    {
        struct virtio_driver *drv;
        drv = container_of(vq->vdev->dev.driver,
                   struct virtio_driver, driver);
        if (drv->config_changed)
            drv->config_changed(vq->vdev);

        break;
    }
    case VIRTIO_PARAM_DEV_ADD:
        schedule_work(&hotplug_work);
        break;
    case VIRTIO_PARAM_VRING_INTERRUPT:
    default:
        vring_interrupt(0, vq);
        break;
    }
}

/*
 * Init function for virtio
 * devices are in a single page above top of "normal" mem
 */
static int __init kvm_devices_init(void)
{
    int rc;

    if (!MACHINE_IS_KVM)
        return -ENODEV;

    kvm_root = root_device_register("kvm_s390");
    if (IS_ERR(kvm_root)) {
        rc = PTR_ERR(kvm_root);
        printk(KERN_ERR "Could not register kvm_s390 root device");
        return rc;
    }

    rc = vmem_add_mapping(real_memory_size, PAGE_SIZE);
    if (rc) {
        root_device_unregister(kvm_root);
        return rc;
    }

    kvm_devices = (void *) real_memory_size;

    INIT_WORK(&hotplug_work, hotplug_devices);

    service_subclass_irq_register();
    register_external_interrupt(0x2603, kvm_extint_handler);

    scan_devices();
    return 0;
}

/* code for early console output with virtio_console */
static __init int early_put_chars(u32 vtermno, const char *buf, int count)
{
    char scratch[17];
    unsigned int len = count;

    if (len > sizeof(scratch) - 1)
        len = sizeof(scratch) - 1;
    scratch[len] = '\0';
    memcpy(scratch, buf, len);
    kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, __pa(scratch));
    return len;
}

static int __init s390_virtio_console_init(void)
{
    if (sclp_has_vt220() || sclp_has_linemode())
        return -ENODEV;
    return virtio_cons_early_init(early_put_chars);
}
console_initcall(s390_virtio_console_init);


/*
 * We do this after core stuff, but before the drivers.
 */
postcore_initcall(kvm_devices_init);