/*
 * Virtio Balloon Device
 *
 * Copyright IBM, Corp. 2008
 * Copyright (C) 2011 Red Hat, Inc.
 * Copyright (C) 2011 Amit Shah <amit.shah@redhat.com>
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "qemu/iov.h"
#include "qemu/timer.h"
#include "qemu-common.h"
#include "virtio.h"
#include "pc.h"
#include "cpu.h"
#include "sysemu/balloon.h"
#include "virtio-balloon.h"
#include "sysemu/kvm.h"
#include "exec/address-spaces.h"
#include "qapi/visitor.h"

#if defined(__linux__)
#include <sys/mman.h>
#endif

typedef struct VirtIOBalloon
{
    VirtIODevice vdev;
    VirtQueue *ivq, *dvq, *svq;
    uint32_t num_pages;
    uint32_t actual;
    uint64_t stats[VIRTIO_BALLOON_S_NR];
    VirtQueueElement stats_vq_elem;
    size_t stats_vq_offset;
    QEMUTimer *stats_timer;
    int64_t stats_last_update;
    int64_t stats_poll_interval;
    DeviceState *qdev;
} VirtIOBalloon;

static VirtIOBalloon *to_virtio_balloon(VirtIODevice *vdev)
{
    return (VirtIOBalloon *)vdev;
}

static void balloon_page(void *addr, int deflate)
{
#if defined(__linux__)
    if (!kvm_enabled() || kvm_has_sync_mmu())
        qemu_madvise(addr, TARGET_PAGE_SIZE,
                deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED);
#endif
}

static const char *balloon_stat_names[] = {
   [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
   [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
   [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
   [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
   [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
   [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
   [VIRTIO_BALLOON_S_NR] = NULL
};

/*
 * reset_stats - Mark all items in the stats array as unset
 *
 * This function needs to be called at device intialization and before
 * before updating to a set of newly-generated stats.  This will ensure that no
 * stale values stick around in case the guest reports a subset of the supported
 * statistics.
 */
static inline void reset_stats(VirtIOBalloon *dev)
{
    int i;
    for (i = 0; i < VIRTIO_BALLOON_S_NR; dev->stats[i++] = -1);
}

static bool balloon_stats_supported(const VirtIOBalloon *s)
{
    return s->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ);
}

static bool balloon_stats_enabled(const VirtIOBalloon *s)
{
    return s->stats_poll_interval > 0;
}

static void balloon_stats_destroy_timer(VirtIOBalloon *s)
{
    if (balloon_stats_enabled(s)) {
        qemu_del_timer(s->stats_timer);
        qemu_free_timer(s->stats_timer);
        s->stats_timer = NULL;
        s->stats_poll_interval = 0;
    }
}

static void balloon_stats_change_timer(VirtIOBalloon *s, int secs)
{
    qemu_mod_timer(s->stats_timer, qemu_get_clock_ms(vm_clock) + secs * 1000);
}

static void balloon_stats_poll_cb(void *opaque)
{
    VirtIOBalloon *s = opaque;

    if (!balloon_stats_supported(s)) {
        /* re-schedule */
        balloon_stats_change_timer(s, s->stats_poll_interval);
        return;
    }

    virtqueue_push(s->svq, &s->stats_vq_elem, s->stats_vq_offset);
    virtio_notify(&s->vdev, s->svq);
}

static void balloon_stats_get_all(Object *obj, struct Visitor *v,
                                  void *opaque, const char *name, Error **errp)
{
    VirtIOBalloon *s = opaque;
    int i;

    if (!s->stats_last_update) {
        error_setg(errp, "guest hasn't updated any stats yet");
        return;
    }

    visit_start_struct(v, NULL, "guest-stats", name, 0, errp);
    visit_type_int(v, &s->stats_last_update, "last-update", errp);

    visit_start_struct(v, NULL, NULL, "stats", 0, errp);
    for (i = 0; i < VIRTIO_BALLOON_S_NR; i++) {
        visit_type_int64(v, (int64_t *) &s->stats[i], balloon_stat_names[i],
                         errp);
    }
    visit_end_struct(v, errp);

    visit_end_struct(v, errp);
}

static void balloon_stats_get_poll_interval(Object *obj, struct Visitor *v,
                                            void *opaque, const char *name,
                                            Error **errp)
{
    VirtIOBalloon *s = opaque;
    visit_type_int(v, &s->stats_poll_interval, name, errp);
}

static void balloon_stats_set_poll_interval(Object *obj, struct Visitor *v,
                                            void *opaque, const char *name,
                                            Error **errp)
{
    VirtIOBalloon *s = opaque;
    int64_t value;

    visit_type_int(v, &value, name, errp);
    if (error_is_set(errp)) {
        return;
    }

    if (value < 0) {
        error_setg(errp, "timer value must be greater than zero");
        return;
    }

    if (value == s->stats_poll_interval) {
        return;
    }

    if (value == 0) {
        /* timer=0 disables the timer */
        balloon_stats_destroy_timer(s);
        return;
    }

    if (balloon_stats_enabled(s)) {
        /* timer interval change */
        s->stats_poll_interval = value;
        balloon_stats_change_timer(s, value);
        return;
    }

    /* create a new timer */
    g_assert(s->stats_timer == NULL);
    s->stats_timer = qemu_new_timer_ms(vm_clock, balloon_stats_poll_cb, s);
    s->stats_poll_interval = value;
    balloon_stats_change_timer(s, 0);
}

static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *s = to_virtio_balloon(vdev);
    VirtQueueElement elem;
    MemoryRegionSection section;

    while (virtqueue_pop(vq, &elem)) {
        size_t offset = 0;
        uint32_t pfn;

        while (iov_to_buf(elem.out_sg, elem.out_num, offset, &pfn, 4) == 4) {
            ram_addr_t pa;
            ram_addr_t addr;

            pa = (ram_addr_t)ldl_p(&pfn) << VIRTIO_BALLOON_PFN_SHIFT;
            offset += 4;

            /* FIXME: remove get_system_memory(), but how? */
            section = memory_region_find(get_system_memory(), pa, 1);
            if (!section.size || !memory_region_is_ram(section.mr))
                continue;

            /* Using memory_region_get_ram_ptr is bending the rules a bit, but
               should be OK because we only want a single page.  */
            addr = section.offset_within_region;
            balloon_page(memory_region_get_ram_ptr(section.mr) + addr,
                         !!(vq == s->dvq));
        }

        virtqueue_push(vq, &elem, offset);
        virtio_notify(vdev, vq);
    }
}

static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *s = DO_UPCAST(VirtIOBalloon, vdev, vdev);
    VirtQueueElement *elem = &s->stats_vq_elem;
    VirtIOBalloonStat stat;
    size_t offset = 0;
    qemu_timeval tv;

    if (!virtqueue_pop(vq, elem)) {
        goto out;
    }

    /* Initialize the stats to get rid of any stale values.  This is only
     * needed to handle the case where a guest supports fewer stats than it
     * used to (ie. it has booted into an old kernel).
     */
    reset_stats(s);

    while (iov_to_buf(elem->out_sg, elem->out_num, offset, &stat, sizeof(stat))
           == sizeof(stat)) {
        uint16_t tag = tswap16(stat.tag);
        uint64_t val = tswap64(stat.val);

        offset += sizeof(stat);
        if (tag < VIRTIO_BALLOON_S_NR)
            s->stats[tag] = val;
    }
    s->stats_vq_offset = offset;

    if (qemu_gettimeofday(&tv) < 0) {
        fprintf(stderr, "warning: %s: failed to get time of day\n", __func__);
        goto out;
    }

    s->stats_last_update = tv.tv_sec;

out:
    if (balloon_stats_enabled(s)) {
        balloon_stats_change_timer(s, s->stats_poll_interval);
    }
}

static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
{
    VirtIOBalloon *dev = to_virtio_balloon(vdev);
    struct virtio_balloon_config config;

    config.num_pages = cpu_to_le32(dev->num_pages);
    config.actual = cpu_to_le32(dev->actual);

    memcpy(config_data, &config, 8);
}

static void virtio_balloon_set_config(VirtIODevice *vdev,
                                      const uint8_t *config_data)
{
    VirtIOBalloon *dev = to_virtio_balloon(vdev);
    struct virtio_balloon_config config;
    uint32_t oldactual = dev->actual;
    memcpy(&config, config_data, 8);
    dev->actual = le32_to_cpu(config.actual);
    if (dev->actual != oldactual) {
        qemu_balloon_changed(ram_size -
                             (dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
    }
}

static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
{
    f |= (1 << VIRTIO_BALLOON_F_STATS_VQ);
    return f;
}

static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
{
    VirtIOBalloon *dev = opaque;
    info->actual = ram_size - ((uint64_t) dev->actual <<
                               VIRTIO_BALLOON_PFN_SHIFT);
}

static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
{
    VirtIOBalloon *dev = opaque;

    if (target > ram_size) {
        target = ram_size;
    }
    if (target) {
        dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
        virtio_notify_config(&dev->vdev);
    }
}

static void virtio_balloon_save(QEMUFile *f, void *opaque)
{
    VirtIOBalloon *s = opaque;

    virtio_save(&s->vdev, f);

    qemu_put_be32(f, s->num_pages);
    qemu_put_be32(f, s->actual);
}

static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
{
    VirtIOBalloon *s = opaque;
    int ret;

    if (version_id != 1)
        return -EINVAL;

    ret = virtio_load(&s->vdev, f);
    if (ret) {
        return ret;
    }

    s->num_pages = qemu_get_be32(f);
    s->actual = qemu_get_be32(f);
    return 0;
}

VirtIODevice *virtio_balloon_init(DeviceState *dev)
{
    VirtIOBalloon *s;
    int ret;

    s = (VirtIOBalloon *)virtio_common_init("virtio-balloon",
                                            VIRTIO_ID_BALLOON,
                                            8, sizeof(VirtIOBalloon));

    s->vdev.get_config = virtio_balloon_get_config;
    s->vdev.set_config = virtio_balloon_set_config;
    s->vdev.get_features = virtio_balloon_get_features;

    ret = qemu_add_balloon_handler(virtio_balloon_to_target,
                                   virtio_balloon_stat, s);
    if (ret < 0) {
        virtio_cleanup(&s->vdev);
        return NULL;
    }

    s->ivq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);
    s->dvq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);
    s->svq = virtio_add_queue(&s->vdev, 128, virtio_balloon_receive_stats);

    s->qdev = dev;
    register_savevm(dev, "virtio-balloon", -1, 1,
                    virtio_balloon_save, virtio_balloon_load, s);

    object_property_add(OBJECT(dev), "guest-stats", "guest statistics",
                        balloon_stats_get_all, NULL, NULL, s, NULL);

    object_property_add(OBJECT(dev), "guest-stats-polling-interval", "int",
                        balloon_stats_get_poll_interval,
                        balloon_stats_set_poll_interval,
                        NULL, s, NULL);

    return &s->vdev;
}

void virtio_balloon_exit(VirtIODevice *vdev)
{
    VirtIOBalloon *s = DO_UPCAST(VirtIOBalloon, vdev, vdev);

    balloon_stats_destroy_timer(s);
    qemu_remove_balloon_handler(s);
    unregister_savevm(s->qdev, "virtio-balloon", s);
    virtio_cleanup(vdev);
}