/*
 * Copyright (C) 2014-2018 Vincenzo Maffione, Luigi Rizzo.
 *
 * 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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

/*
 */

#include <net/netmap.h>
#include <sys/selinfo.h>
#include <vm/vm.h>
#include <vm/pmap.h>    /* vtophys ? */
#include <dev/netmap/netmap_kern.h>

/* Register and unregister. */
static int
vtnet_netmap_reg(struct netmap_adapter *na, int state)
{
        if_t ifp = na->ifp;
        struct vtnet_softc *sc = if_getsoftc(ifp);

        /*
         * Trigger a device reinit, asking vtnet_init_locked() to
         * also enter or exit netmap mode.
         */
        VTNET_CORE_LOCK(sc);
        if_setdrvflagbits(ifp, 0, IFF_DRV_RUNNING);
        vtnet_init_locked(sc, state ? VTNET_INIT_NETMAP_ENTER
            : VTNET_INIT_NETMAP_EXIT);
        VTNET_CORE_UNLOCK(sc);

        return (0);
}


/* Reconcile kernel and user view of the transmit ring. */
static int
vtnet_netmap_txsync(struct netmap_kring *kring, int flags)
{
        struct netmap_adapter *na = kring->na;
        if_t ifp = na->ifp;
        struct netmap_ring *ring = kring->ring;
        u_int ring_nr = kring->ring_id;
        u_int nm_i;     /* index into the netmap ring */
        u_int const lim = kring->nkr_num_slots - 1;
        u_int const head = kring->rhead;

        /* device-specific */
        struct vtnet_softc *sc = if_getsoftc(ifp);
        struct vtnet_txq *txq = &sc->vtnet_txqs[ring_nr];
        struct virtqueue *vq = txq->vtntx_vq;
        int interrupts = !(kring->nr_kflags & NKR_NOINTR);
        u_int n;

        /*
         * First part: process new packets to send.
         */

        nm_i = kring->nr_hwcur;
        if (nm_i != head) {     /* we have new packets to send */
                struct sglist *sg = txq->vtntx_sg;

                for (; nm_i != head; nm_i = nm_next(nm_i, lim)) {
                        /* we use an empty header here */
                        struct netmap_slot *slot = &ring->slot[nm_i];
                        uint64_t offset = nm_get_offset(kring, slot);
                        u_int len = slot->len;
                        uint64_t paddr;
                        int err;

                        (void)PNMB(na, slot, &paddr);
                        NM_CHECK_ADDR_LEN_OFF(na, len, offset);

                        slot->flags &= ~(NS_REPORT | NS_BUF_CHANGED);
                        /* Initialize the scatterlist, expose it to the hypervisor,
                         * and kick the hypervisor (if necessary).
                         */
                        sglist_reset(sg); // cheap
                        err = sglist_append(sg, &txq->vtntx_shrhdr, sc->vtnet_hdr_size);
                        err |= sglist_append_phys(sg, paddr + offset, len);
                        KASSERT(err == 0, ("%s: cannot append to sglist %d",
                                                __func__, err));
                        err = virtqueue_enqueue(vq, /*cookie=*/txq, sg,
                                                /*readable=*/sg->sg_nseg,
                                                /*writeable=*/0);
                        if (unlikely(err)) {
                                if (err != ENOSPC)
                                        nm_prerr("virtqueue_enqueue(%s) failed: %d",
                                                        kring->name, err);
                                break;
                        }
                }

                virtqueue_notify(vq);

                /* Update hwcur depending on where we stopped. */
                kring->nr_hwcur = nm_i; /* note we might break early */
        }

        /* Free used slots. We only consider our own used buffers, recognized
         * by the token we passed to virtqueue_enqueue.
         */
        n = 0;
        for (;;) {
                void *token = virtqueue_dequeue(vq, NULL);
                if (token == NULL)
                        break;
                if (unlikely(token != (void *)txq))
                        nm_prerr("BUG: TX token mismatch");
                else
                        n++;
        }
        if (n > 0) {
                kring->nr_hwtail += n;
                if (kring->nr_hwtail > lim)
                        kring->nr_hwtail -= lim + 1;
        }

        if (interrupts && virtqueue_nfree(vq) < 32)
                virtqueue_postpone_intr(vq, VQ_POSTPONE_LONG);

        return 0;
}

/*
 * Publish 'num 'netmap receive buffers to the host, starting
 * from the next available one (rx->vtnrx_nm_refill).
 * Return a positive error code on error, and 0 on success.
 * If we could not publish all of the buffers that's an error,
 * since the netmap ring and the virtqueue would go out of sync.
 */
static int
vtnet_netmap_kring_refill(struct netmap_kring *kring, u_int num)
{
        struct netmap_adapter *na = kring->na;
        if_t ifp = na->ifp;
        struct netmap_ring *ring = kring->ring;
        u_int ring_nr = kring->ring_id;
        u_int const lim = kring->nkr_num_slots - 1;
        u_int nm_i;

        /* device-specific */
        struct vtnet_softc *sc = if_getsoftc(ifp);
        struct vtnet_rxq *rxq = &sc->vtnet_rxqs[ring_nr];
        struct virtqueue *vq = rxq->vtnrx_vq;

        /* use a local sglist, default might be short */
        struct sglist_seg ss[2];
        struct sglist sg = { ss, 0, 0, 2 };

        for (nm_i = rxq->vtnrx_nm_refill; num > 0;
            nm_i = nm_next(nm_i, lim), num--) {
                struct netmap_slot *slot = &ring->slot[nm_i];
                uint64_t offset = nm_get_offset(kring, slot);
                uint64_t paddr;
                void *addr = PNMB(na, slot, &paddr);
                int err;

                if (addr == NETMAP_BUF_BASE(na)) { /* bad buf */
                        netmap_ring_reinit(kring);
                        return EFAULT;
                }

                slot->flags &= ~NS_BUF_CHANGED;
                sglist_reset(&sg);
                err = sglist_append(&sg, &rxq->vtnrx_shrhdr, sc->vtnet_hdr_size);
                err |= sglist_append_phys(&sg, paddr + offset,
                    NETMAP_BUF_SIZE(na) - offset);
                KASSERT(err == 0, ("%s: cannot append to sglist %d",
                                        __func__, err));
                /* writable for the host */
                err = virtqueue_enqueue(vq, /*cookie=*/rxq, &sg,
                                /*readable=*/0, /*writeable=*/sg.sg_nseg);
                if (unlikely(err)) {
                        nm_prerr("virtqueue_enqueue(%s) failed: %d",
                                kring->name, err);
                        break;
                }
        }
        rxq->vtnrx_nm_refill = nm_i;

        return num == 0 ? 0 : ENOSPC;
}

/*
 * Publish netmap buffers on a RX virtqueue.
 * Returns -1 if this virtqueue is not being opened in netmap mode.
 * If the virtqueue is being opened in netmap mode, return 0 on success and
 * a positive error code on failure.
 */
static int
vtnet_netmap_rxq_populate(struct vtnet_rxq *rxq)
{
        struct netmap_adapter *na = NA(rxq->vtnrx_sc->vtnet_ifp);
        struct netmap_kring *kring;
        struct netmap_slot *slot;
        int error;
        int num;

        slot = netmap_reset(na, NR_RX, rxq->vtnrx_id, 0);
        if (slot == NULL)
                return -1;
        kring = na->rx_rings[rxq->vtnrx_id];

        /*
         * Expose all the RX netmap buffers we can. In case of no indirect
         * buffers, the number of netmap slots in the RX ring matches the
         * maximum number of 2-elements sglist that the RX virtqueue can
         * accommodate. We need to start from kring->nr_hwtail, which is 0
         * on the first netmap register and may be different from 0 if a
         * virtio re-init (caused by a netma register or i.e., ifconfig)
         * happens while the device is in use by netmap.
         */
        rxq->vtnrx_nm_refill = kring->nr_hwtail;
        num = na->num_rx_desc - 1 - nm_kr_rxspace(kring);
        error = vtnet_netmap_kring_refill(kring, num);
        virtqueue_notify(rxq->vtnrx_vq);

        return error;
}

/* Reconcile kernel and user view of the receive ring. */
static int
vtnet_netmap_rxsync(struct netmap_kring *kring, int flags)
{
        struct netmap_adapter *na = kring->na;
        if_t ifp = na->ifp;
        struct netmap_ring *ring = kring->ring;
        u_int ring_nr = kring->ring_id;
        u_int nm_i;     /* index into the netmap ring */
        u_int const lim = kring->nkr_num_slots - 1;
        u_int const head = kring->rhead;
        int force_update = (flags & NAF_FORCE_READ) ||
                                (kring->nr_kflags & NKR_PENDINTR);
        int interrupts = !(kring->nr_kflags & NKR_NOINTR);

        /* device-specific */
        struct vtnet_softc *sc = if_getsoftc(ifp);
        struct vtnet_rxq *rxq = &sc->vtnet_rxqs[ring_nr];
        struct virtqueue *vq = rxq->vtnrx_vq;

        /*
         * First part: import newly received packets.
         * Only accept our own buffers (matching the token). We should only get
         * matching buffers. The hwtail should never overrun hwcur, because
         * we publish only N-1 receive buffers (and not N).
         * In any case we must not leave this routine with the interrupts
         * disabled, pending packets in the VQ and hwtail == (hwcur - 1),
         * otherwise the pending packets could stall.
         */
        if (netmap_no_pendintr || force_update) {
                uint32_t hwtail_lim = nm_prev(kring->nr_hwcur, lim);
                void *token;

                vtnet_rxq_disable_intr(rxq);

                nm_i = kring->nr_hwtail;
                for (;;) {
                        int len;
                        token = virtqueue_dequeue(vq, &len);
                        if (token == NULL) {
                                /*
                                 * Enable the interrupts again and double-check
                                 * for more work. We can go on until we win the
                                 * race condition, since we are not replenishing
                                 * in the meanwhile, and thus we will process at
                                 * most N-1 slots.
                                 */
                                if (interrupts && vtnet_rxq_enable_intr(rxq)) {
                                        vtnet_rxq_disable_intr(rxq);
                                        continue;
                                }
                                break;
                        }
                        if (unlikely(token != (void *)rxq)) {
                                nm_prerr("BUG: RX token mismatch");
                        } else {
                                if (nm_i == hwtail_lim) {
                                        KASSERT(false, ("hwtail would "
                                            "overrun hwcur"));
                                }

                                /* Skip the virtio-net header. */
                                len -= sc->vtnet_hdr_size;
                                if (unlikely(len < 0)) {
                                        nm_prlim(1, "Truncated virtio-net-header, "
                                                "missing %d bytes", -len);
                                        len = 0;
                                }
                                ring->slot[nm_i].len = len;
                                ring->slot[nm_i].flags = 0;
                                nm_i = nm_next(nm_i, lim);
                        }
                }
                kring->nr_hwtail = nm_i;
                kring->nr_kflags &= ~NKR_PENDINTR;
        }

        /*
         * Second part: skip past packets that userspace has released.
         */
        nm_i = kring->nr_hwcur; /* netmap ring index */
        if (nm_i != head) {
                int released;
                int error;

                released = head - nm_i;
                if (released < 0)
                        released += kring->nkr_num_slots;
                error = vtnet_netmap_kring_refill(kring, released);
                if (error) {
                        nm_prerr("Failed to replenish RX VQ with %u sgs",
                            released);
                        return error;
                }
                kring->nr_hwcur = head;
                virtqueue_notify(vq);
        }

        nm_prdis("h %d c %d t %d hwcur %d hwtail %d", kring->rhead,
            kring->rcur, kring->rtail, kring->nr_hwcur, kring->nr_hwtail);

        return 0;
}


/* Enable/disable interrupts on all virtqueues. */
static void
vtnet_netmap_intr(struct netmap_adapter *na, int state)
{
        struct vtnet_softc *sc = if_getsoftc(na->ifp);
        int i;

        for (i = 0; i < sc->vtnet_max_vq_pairs; i++) {
                struct vtnet_rxq *rxq = &sc->vtnet_rxqs[i];
                struct vtnet_txq *txq = &sc->vtnet_txqs[i];
                struct virtqueue *txvq = txq->vtntx_vq;

                if (state) {
                        vtnet_rxq_enable_intr(rxq);
                        virtqueue_enable_intr(txvq);
                } else {
                        vtnet_rxq_disable_intr(rxq);
                        virtqueue_disable_intr(txvq);
                }
        }
}

static int
vtnet_netmap_tx_slots(struct vtnet_softc *sc)
{
        int div;

        /* We need to prepend a virtio-net header to each netmap buffer to be
         * transmitted, therefore calling virtqueue_enqueue() passing sglist
         * with 2 elements.
         * TX virtqueues use indirect descriptors if the feature was negotiated
         * with the host, and if sc->vtnet_tx_nsegs > 1. With indirect
         * descriptors, a single virtio descriptor is sufficient to reference
         * each TX sglist. Without them, we need two separate virtio descriptors
         * for each TX sglist. We therefore compute the number of netmap TX
         * slots according to these assumptions.
         */
        if ((sc->vtnet_flags & VTNET_FLAG_INDIRECT) && sc->vtnet_tx_nsegs > 1)
                div = 1;
        else
                div = 2;

        return virtqueue_size(sc->vtnet_txqs[0].vtntx_vq) / div;
}

static int
vtnet_netmap_rx_slots(struct vtnet_softc *sc)
{
        int div;

        /* We need to prepend a virtio-net header to each netmap buffer to be
         * received, therefore calling virtqueue_enqueue() passing sglist
         * with 2 elements.
         * RX virtqueues use indirect descriptors if the feature was negotiated
         * with the host, and if sc->vtnet_rx_nsegs > 1. With indirect
         * descriptors, a single virtio descriptor is sufficient to reference
         * each RX sglist. Without them, we need two separate virtio descriptors
         * for each RX sglist. We therefore compute the number of netmap RX
         * slots according to these assumptions.
         */
        if ((sc->vtnet_flags & VTNET_FLAG_INDIRECT) && sc->vtnet_rx_nsegs > 1)
                div = 1;
        else
                div = 2;

        return virtqueue_size(sc->vtnet_rxqs[0].vtnrx_vq) / div;
}

static int
vtnet_netmap_config(struct netmap_adapter *na, struct nm_config_info *info)
{
        struct vtnet_softc *sc = if_getsoftc(na->ifp);

        info->num_tx_rings = sc->vtnet_act_vq_pairs;
        info->num_rx_rings = sc->vtnet_act_vq_pairs;
        info->num_tx_descs = vtnet_netmap_tx_slots(sc);
        info->num_rx_descs = vtnet_netmap_rx_slots(sc);
        info->rx_buf_maxsize = NETMAP_BUF_SIZE(na);

        return 0;
}

static void
vtnet_netmap_attach(struct vtnet_softc *sc)
{
        struct netmap_adapter na;

        bzero(&na, sizeof(na));

        na.ifp = sc->vtnet_ifp;
        na.na_flags = NAF_OFFSETS;
        na.num_tx_desc = vtnet_netmap_tx_slots(sc);
        na.num_rx_desc = vtnet_netmap_rx_slots(sc);
        na.num_tx_rings = na.num_rx_rings = sc->vtnet_max_vq_pairs;
        na.rx_buf_maxsize = 0;
        na.nm_register = vtnet_netmap_reg;
        na.nm_txsync = vtnet_netmap_txsync;
        na.nm_rxsync = vtnet_netmap_rxsync;
        na.nm_intr = vtnet_netmap_intr;
        na.nm_config = vtnet_netmap_config;

        netmap_attach(&na);

        nm_prinf("vtnet attached txq=%d, txd=%d rxq=%d, rxd=%d",
                        na.num_tx_rings, na.num_tx_desc,
                        na.num_tx_rings, na.num_rx_desc);
}
/* end of file */