/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011, Bryan Venteicher <bryanv@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* Driver for VirtIO memory balloon devices. */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/endian.h>
#include <sys/kthread.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/sglist.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/queue.h>

#include <vm/vm.h>
#include <vm/vm_page.h>

#include <machine/bus.h>
#include <machine/resource.h>
#include <sys/bus.h>
#include <sys/rman.h>

#include <dev/virtio/virtio.h>
#include <dev/virtio/virtqueue.h>
#include <dev/virtio/balloon/virtio_balloon.h>

#include "virtio_if.h"

struct vtballoon_softc {
        device_t                 vtballoon_dev;
        struct mtx               vtballoon_mtx;
        uint64_t                 vtballoon_features;
        uint32_t                 vtballoon_flags;
#define VTBALLOON_FLAG_DETACH    0x01

        struct virtqueue        *vtballoon_inflate_vq;
        struct virtqueue        *vtballoon_deflate_vq;

        uint32_t                 vtballoon_desired_npages;
        uint32_t                 vtballoon_current_npages;
        TAILQ_HEAD(,vm_page)     vtballoon_pages;

        struct thread           *vtballoon_td;
        uint32_t                *vtballoon_page_frames;
        int                      vtballoon_timeout;
};

static struct virtio_feature_desc vtballoon_feature_desc[] = {
        { VIRTIO_BALLOON_F_MUST_TELL_HOST,      "MustTellHost"  },
        { VIRTIO_BALLOON_F_STATS_VQ,            "StatsVq"       },
        { VIRTIO_BALLOON_F_DEFLATE_ON_OOM,      "DeflateOnOOM"  },

        { 0, NULL }
};

static int      vtballoon_probe(device_t);
static int      vtballoon_attach(device_t);
static int      vtballoon_detach(device_t);
static int      vtballoon_config_change(device_t);

static int      vtballoon_negotiate_features(struct vtballoon_softc *);
static int      vtballoon_setup_features(struct vtballoon_softc *);
static int      vtballoon_alloc_virtqueues(struct vtballoon_softc *);

static void     vtballoon_vq_intr(void *);

static void     vtballoon_inflate(struct vtballoon_softc *, int);
static void     vtballoon_deflate(struct vtballoon_softc *, int);

static void     vtballoon_send_page_frames(struct vtballoon_softc *,
                    struct virtqueue *, int);

static void     vtballoon_pop(struct vtballoon_softc *);
static void     vtballoon_stop(struct vtballoon_softc *);

static vm_page_t
                vtballoon_alloc_page(struct vtballoon_softc *);
static void     vtballoon_free_page(struct vtballoon_softc *, vm_page_t);

static int      vtballoon_sleep(struct vtballoon_softc *);
static void     vtballoon_thread(void *);
static void     vtballoon_setup_sysctl(struct vtballoon_softc *);

#define vtballoon_modern(_sc) \
    (((_sc)->vtballoon_features & VIRTIO_F_VERSION_1) != 0)

/* Features desired/implemented by this driver. */
#define VTBALLOON_FEATURES              VIRTIO_BALLOON_F_MUST_TELL_HOST

/* Timeout between retries when the balloon needs inflating. */
#define VTBALLOON_LOWMEM_TIMEOUT        hz

/*
 * Maximum number of pages we'll request to inflate or deflate
 * the balloon in one virtqueue request. Both Linux and NetBSD
 * have settled on 256, doing up to 1MB at a time.
 */
#define VTBALLOON_PAGES_PER_REQUEST     256

/* Must be able to fix all pages frames in one page (segment). */
CTASSERT(VTBALLOON_PAGES_PER_REQUEST * sizeof(uint32_t) <= PAGE_SIZE);

#define VTBALLOON_MTX(_sc)              &(_sc)->vtballoon_mtx
#define VTBALLOON_LOCK_INIT(_sc, _name) mtx_init(VTBALLOON_MTX((_sc)), _name, \
                                            "VirtIO Balloon Lock", MTX_DEF)
#define VTBALLOON_LOCK(_sc)             mtx_lock(VTBALLOON_MTX((_sc)))
#define VTBALLOON_UNLOCK(_sc)           mtx_unlock(VTBALLOON_MTX((_sc)))
#define VTBALLOON_LOCK_DESTROY(_sc)     mtx_destroy(VTBALLOON_MTX((_sc)))

static device_method_t vtballoon_methods[] = {
        /* Device methods. */
        DEVMETHOD(device_probe,         vtballoon_probe),
        DEVMETHOD(device_attach,        vtballoon_attach),
        DEVMETHOD(device_detach,        vtballoon_detach),

        /* VirtIO methods. */
        DEVMETHOD(virtio_config_change, vtballoon_config_change),

        DEVMETHOD_END
};

static driver_t vtballoon_driver = {
        "vtballoon",
        vtballoon_methods,
        sizeof(struct vtballoon_softc)
};

VIRTIO_DRIVER_MODULE(virtio_balloon, vtballoon_driver, 0, 0);
MODULE_VERSION(virtio_balloon, 1);
MODULE_DEPEND(virtio_balloon, virtio, 1, 1, 1);

VIRTIO_SIMPLE_PNPINFO(virtio_balloon, VIRTIO_ID_BALLOON,
    "VirtIO Balloon Adapter");

static int
vtballoon_probe(device_t dev)
{
        return (VIRTIO_SIMPLE_PROBE(dev, virtio_balloon));
}

static int
vtballoon_attach(device_t dev)
{
        struct vtballoon_softc *sc;
        int error;

        sc = device_get_softc(dev);
        sc->vtballoon_dev = dev;
        virtio_set_feature_desc(dev, vtballoon_feature_desc);

        VTBALLOON_LOCK_INIT(sc, device_get_nameunit(dev));
        TAILQ_INIT(&sc->vtballoon_pages);

        vtballoon_setup_sysctl(sc);

        error = vtballoon_setup_features(sc);
        if (error) {
                device_printf(dev, "cannot setup features\n");
                goto fail;
        }

        sc->vtballoon_page_frames = malloc(VTBALLOON_PAGES_PER_REQUEST *
            sizeof(uint32_t), M_DEVBUF, M_NOWAIT | M_ZERO);
        if (sc->vtballoon_page_frames == NULL) {
                error = ENOMEM;
                device_printf(dev,
                    "cannot allocate page frame request array\n");
                goto fail;
        }

        error = vtballoon_alloc_virtqueues(sc);
        if (error) {
                device_printf(dev, "cannot allocate virtqueues\n");
                goto fail;
        }

        error = virtio_setup_intr(dev, INTR_TYPE_MISC);
        if (error) {
                device_printf(dev, "cannot setup virtqueue interrupts\n");
                goto fail;
        }

        error = kthread_add(vtballoon_thread, sc, NULL, &sc->vtballoon_td,
            0, 0, "virtio_balloon");
        if (error) {
                device_printf(dev, "cannot create balloon kthread\n");
                goto fail;
        }

        virtqueue_enable_intr(sc->vtballoon_inflate_vq);
        virtqueue_enable_intr(sc->vtballoon_deflate_vq);

fail:
        if (error)
                vtballoon_detach(dev);

        return (error);
}

static int
vtballoon_detach(device_t dev)
{
        struct vtballoon_softc *sc;

        sc = device_get_softc(dev);

        if (sc->vtballoon_td != NULL) {
                VTBALLOON_LOCK(sc);
                sc->vtballoon_flags |= VTBALLOON_FLAG_DETACH;
                wakeup_one(sc);
                msleep(sc->vtballoon_td, VTBALLOON_MTX(sc), 0, "vtbdth", 0);
                VTBALLOON_UNLOCK(sc);

                sc->vtballoon_td = NULL;
        }

        if (device_is_attached(dev)) {
                vtballoon_pop(sc);
                vtballoon_stop(sc);
        }

        if (sc->vtballoon_page_frames != NULL) {
                free(sc->vtballoon_page_frames, M_DEVBUF);
                sc->vtballoon_page_frames = NULL;
        }

        VTBALLOON_LOCK_DESTROY(sc);

        return (0);
}

static int
vtballoon_config_change(device_t dev)
{
        struct vtballoon_softc *sc;

        sc = device_get_softc(dev);

        VTBALLOON_LOCK(sc);
        wakeup_one(sc);
        VTBALLOON_UNLOCK(sc);

        return (1);
}

static int
vtballoon_negotiate_features(struct vtballoon_softc *sc)
{
        device_t dev;
        uint64_t features;

        dev = sc->vtballoon_dev;
        features = VTBALLOON_FEATURES;

        sc->vtballoon_features = virtio_negotiate_features(dev, features);
        return (virtio_finalize_features(dev));
}

static int
vtballoon_setup_features(struct vtballoon_softc *sc)
{
        int error;

        error = vtballoon_negotiate_features(sc);
        if (error)
                return (error);

        return (0);
}

static int
vtballoon_alloc_virtqueues(struct vtballoon_softc *sc)
{
        device_t dev;
        struct vq_alloc_info vq_info[2];
        int nvqs;

        dev = sc->vtballoon_dev;
        nvqs = 2;

        VQ_ALLOC_INFO_INIT(&vq_info[0], 0, vtballoon_vq_intr, sc,
            &sc->vtballoon_inflate_vq, "%s inflate", device_get_nameunit(dev));

        VQ_ALLOC_INFO_INIT(&vq_info[1], 0, vtballoon_vq_intr, sc,
            &sc->vtballoon_deflate_vq, "%s deflate", device_get_nameunit(dev));

        return (virtio_alloc_virtqueues(dev, nvqs, vq_info));
}

static void
vtballoon_vq_intr(void *xsc)
{
        struct vtballoon_softc *sc;

        sc = xsc;

        VTBALLOON_LOCK(sc);
        wakeup_one(sc);
        VTBALLOON_UNLOCK(sc);
}

static void
vtballoon_inflate(struct vtballoon_softc *sc, int npages)
{
        struct virtqueue *vq;
        vm_page_t m;
        int i;

        vq = sc->vtballoon_inflate_vq;

        if (npages > VTBALLOON_PAGES_PER_REQUEST)
                npages = VTBALLOON_PAGES_PER_REQUEST;

        for (i = 0; i < npages; i++) {
                if ((m = vtballoon_alloc_page(sc)) == NULL) {
                        sc->vtballoon_timeout = VTBALLOON_LOWMEM_TIMEOUT;
                        break;
                }

                sc->vtballoon_page_frames[i] =
                    VM_PAGE_TO_PHYS(m) >> VIRTIO_BALLOON_PFN_SHIFT;

                KASSERT(m->a.queue == PQ_NONE,
                    ("%s: allocated page %p on queue", __func__, m));
                TAILQ_INSERT_TAIL(&sc->vtballoon_pages, m, plinks.q);
        }

        if (i > 0)
                vtballoon_send_page_frames(sc, vq, i);
}

static void
vtballoon_deflate(struct vtballoon_softc *sc, int npages)
{
        TAILQ_HEAD(, vm_page) free_pages;
        struct virtqueue *vq;
        vm_page_t m;
        int i;

        vq = sc->vtballoon_deflate_vq;
        TAILQ_INIT(&free_pages);

        if (npages > VTBALLOON_PAGES_PER_REQUEST)
                npages = VTBALLOON_PAGES_PER_REQUEST;

        for (i = 0; i < npages; i++) {
                m = TAILQ_FIRST(&sc->vtballoon_pages);
                KASSERT(m != NULL, ("%s: no more pages to deflate", __func__));

                sc->vtballoon_page_frames[i] =
                    VM_PAGE_TO_PHYS(m) >> VIRTIO_BALLOON_PFN_SHIFT;

                TAILQ_REMOVE(&sc->vtballoon_pages, m, plinks.q);
                TAILQ_INSERT_TAIL(&free_pages, m, plinks.q);
        }

        if (i > 0) {
                /* Always tell host first before freeing the pages. */
                vtballoon_send_page_frames(sc, vq, i);

                while ((m = TAILQ_FIRST(&free_pages)) != NULL) {
                        TAILQ_REMOVE(&free_pages, m, plinks.q);
                        vtballoon_free_page(sc, m);
                }
        }

        KASSERT((TAILQ_EMPTY(&sc->vtballoon_pages) &&
            sc->vtballoon_current_npages == 0) ||
            (!TAILQ_EMPTY(&sc->vtballoon_pages) &&
            sc->vtballoon_current_npages != 0),
            ("%s: bogus page count %d", __func__,
            sc->vtballoon_current_npages));
}

static void
vtballoon_send_page_frames(struct vtballoon_softc *sc, struct virtqueue *vq,
    int npages)
{
        struct sglist sg;
        struct sglist_seg segs[1];
        void *c;
        int error __diagused;

        sglist_init(&sg, 1, segs);

        error = sglist_append(&sg, sc->vtballoon_page_frames,
            npages * sizeof(uint32_t));
        KASSERT(error == 0, ("error adding page frames to sglist"));

        error = virtqueue_enqueue(vq, vq, &sg, 1, 0);
        KASSERT(error == 0, ("error enqueuing page frames to virtqueue"));
        virtqueue_notify(vq);

        /*
         * Inflate and deflate operations are done synchronously. The
         * interrupt handler will wake us up.
         */
        VTBALLOON_LOCK(sc);
        while ((c = virtqueue_dequeue(vq, NULL)) == NULL)
                msleep(sc, VTBALLOON_MTX(sc), 0, "vtbspf", 0);
        VTBALLOON_UNLOCK(sc);

        KASSERT(c == vq, ("unexpected balloon operation response"));
}

static void
vtballoon_pop(struct vtballoon_softc *sc)
{

        while (!TAILQ_EMPTY(&sc->vtballoon_pages))
                vtballoon_deflate(sc, sc->vtballoon_current_npages);
}

static void
vtballoon_stop(struct vtballoon_softc *sc)
{

        virtqueue_disable_intr(sc->vtballoon_inflate_vq);
        virtqueue_disable_intr(sc->vtballoon_deflate_vq);

        virtio_stop(sc->vtballoon_dev);
}

static vm_page_t
vtballoon_alloc_page(struct vtballoon_softc *sc)
{
        vm_page_t m;

        m = vm_page_alloc_noobj(VM_ALLOC_NODUMP);
        if (m != NULL)
                sc->vtballoon_current_npages++;

        return (m);
}

static void
vtballoon_free_page(struct vtballoon_softc *sc, vm_page_t m)
{

        vm_page_free(m);
        sc->vtballoon_current_npages--;
}

static uint32_t
vtballoon_desired_size(struct vtballoon_softc *sc)
{
        uint32_t desired;

        desired = virtio_read_dev_config_4(sc->vtballoon_dev,
            offsetof(struct virtio_balloon_config, num_pages));

        if (vtballoon_modern(sc))
                return (desired);
        else
                return (le32toh(desired));
}

static void
vtballoon_update_size(struct vtballoon_softc *sc)
{
        uint32_t npages;

        npages = sc->vtballoon_current_npages;
        if (!vtballoon_modern(sc))
                npages = htole32(npages);

        virtio_write_dev_config_4(sc->vtballoon_dev,
            offsetof(struct virtio_balloon_config, actual), npages);
}

static int
vtballoon_sleep(struct vtballoon_softc *sc)
{
        int rc, timeout;
        uint32_t current, desired;

        rc = 0;
        current = sc->vtballoon_current_npages;

        VTBALLOON_LOCK(sc);
        for (;;) {
                if (sc->vtballoon_flags & VTBALLOON_FLAG_DETACH) {
                        rc = 1;
                        break;
                }

                desired = vtballoon_desired_size(sc);
                sc->vtballoon_desired_npages = desired;

                /*
                 * If given, use non-zero timeout on the first time through
                 * the loop. On subsequent times, timeout will be zero so
                 * we will reevaluate the desired size of the balloon and
                 * break out to retry if needed.
                 */
                timeout = sc->vtballoon_timeout;
                sc->vtballoon_timeout = 0;

                if (current > desired)
                        break;
                if (current < desired && timeout == 0)
                        break;

                msleep(sc, VTBALLOON_MTX(sc), 0, "vtbslp", timeout);
        }
        VTBALLOON_UNLOCK(sc);

        return (rc);
}

static void
vtballoon_thread(void *xsc)
{
        struct vtballoon_softc *sc;
        uint32_t current, desired;

        sc = xsc;

        for (;;) {
                if (vtballoon_sleep(sc) != 0)
                        break;

                current = sc->vtballoon_current_npages;
                desired = sc->vtballoon_desired_npages;

                if (desired != current) {
                        if (desired > current)
                                vtballoon_inflate(sc, desired - current);
                        else
                                vtballoon_deflate(sc, current - desired);

                        vtballoon_update_size(sc);
                }
        }

        kthread_exit();
}

static void
vtballoon_setup_sysctl(struct vtballoon_softc *sc)
{
        device_t dev;
        struct sysctl_ctx_list *ctx;
        struct sysctl_oid *tree;
        struct sysctl_oid_list *child;

        dev = sc->vtballoon_dev;
        ctx = device_get_sysctl_ctx(dev);
        tree = device_get_sysctl_tree(dev);
        child = SYSCTL_CHILDREN(tree);

        SYSCTL_ADD_UINT(ctx, child, OID_AUTO, "desired",
            CTLFLAG_RD, &sc->vtballoon_desired_npages, sizeof(uint32_t),
            "Desired balloon size in pages");

        SYSCTL_ADD_UINT(ctx, child, OID_AUTO, "current",
            CTLFLAG_RD, &sc->vtballoon_current_npages, sizeof(uint32_t),
            "Current balloon size in pages");
}