/*
 * kvm_virtio.c - 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 <borntraeger@de.ibm.com>
 */

#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/pfn.h>
#include <asm/io.h>
#include <asm/kvm_para.h>
#include <asm/kvm_virtio.h>
#include <asm/setup.h>
#include <asm/s390_ext.h>

#define VIRTIO_SUBCODE_64 0x0D00

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

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);

        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(config->num, KVM_S390_VIRTIO_RING_ALIGN,
                                 vdev, (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]);
}

/*
 * 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,
};

/*
 * 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);
        }
}

/*
 * we emulate the request_irq behaviour on top of s390 extints
 */
static void kvm_extint_handler(u16 code)
{
        struct virtqueue *vq;
        u16 subcode;
        int config_changed;

        subcode = S390_lowcore.cpu_addr;
        if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
                return;

        /* The LSB might be overloaded, we have to mask it */
        vq = (struct virtqueue *)(S390_lowcore.ext_params2 & ~1UL);

        /* We use the LSB of extparam, to decide, if this interrupt is a config
         * change or a "standard" interrupt */
        config_changed = S390_lowcore.ext_params & 1;

        if (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);
        } else
                vring_interrupt(0, vq);
}

/*
 * 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;

        ctl_set_bit(0, 9);
        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 (!MACHINE_IS_KVM)
                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);