/*
 * Copyright (C) 2016-2018 Vincenzo Maffione
 * Copyright (C) 2015 Stefano Garzarella
 * 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, 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.
 */

/*
 * common headers
 */
#if defined(__FreeBSD__)

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/types.h>
#include <sys/selinfo.h>
#include <sys/socket.h>
#include <net/if.h>
#include <net/if_var.h>
#include <machine/bus.h>

#define usleep_range(_1, _2) \
        pause_sbt("sync-kloop-sleep", SBT_1US * _1, SBT_1US * 1, C_ABSOLUTE)

#elif defined(linux)
#include <bsd_glue.h>
#include <linux/file.h>
#include <linux/eventfd.h>
#endif

#include <net/netmap.h>
#include <dev/netmap/netmap_kern.h>
#include <net/netmap_virt.h>
#include <dev/netmap/netmap_mem2.h>

/* Support for eventfd-based notifications. */
#if defined(linux)
#define SYNC_KLOOP_POLL
#endif

/* Write kring pointers (hwcur, hwtail) to the CSB.
 * This routine is coupled with ptnetmap_guest_read_kring_csb(). */
static inline void
sync_kloop_kernel_write(struct nm_csb_ktoa __user *ptr, uint32_t hwcur,
                           uint32_t hwtail)
{
        /* Issue a first store-store barrier to make sure writes to the
         * netmap ring do not overcome updates on ktoa->hwcur and ktoa->hwtail. */
        nm_stst_barrier();

        /*
         * The same scheme used in nm_sync_kloop_appl_write() applies here.
         * We allow the application to read a value of hwcur more recent than the value
         * of hwtail, since this would anyway result in a consistent view of the
         * ring state (and hwcur can never wraparound hwtail, since hwcur must be
         * behind head).
         *
         * The following memory barrier scheme is used to make this happen:
         *
         *          Application            Kernel
         *
         *          STORE(hwcur)           LOAD(hwtail)
         *          wmb() <------------->  rmb()
         *          STORE(hwtail)          LOAD(hwcur)
         */
        CSB_WRITE(ptr, hwcur, hwcur);
        nm_stst_barrier();
        CSB_WRITE(ptr, hwtail, hwtail);
}

/* Read kring pointers (head, cur, sync_flags) from the CSB.
 * This routine is coupled with ptnetmap_guest_write_kring_csb(). */
static inline void
sync_kloop_kernel_read(struct nm_csb_atok __user *ptr,
                          struct netmap_ring *shadow_ring,
                          uint32_t num_slots)
{
        /*
         * We place a memory barrier to make sure that the update of head never
         * overtakes the update of cur.
         * (see explanation in sync_kloop_kernel_write).
         */
        CSB_READ(ptr, head, shadow_ring->head);
        nm_ldld_barrier();
        CSB_READ(ptr, cur, shadow_ring->cur);
        CSB_READ(ptr, sync_flags, shadow_ring->flags);

        /* Make sure that loads from atok->head and atok->cur are not delayed
         * after the loads from the netmap ring. */
        nm_ldld_barrier();
}

/* Enable or disable application --> kernel kicks. */
static inline void
csb_ktoa_kick_enable(struct nm_csb_ktoa __user *csb_ktoa, uint32_t val)
{
        CSB_WRITE(csb_ktoa, kern_need_kick, val);
}

#ifdef SYNC_KLOOP_POLL
/* Are application interrupt enabled or disabled? */
static inline uint32_t
csb_atok_intr_enabled(struct nm_csb_atok __user *csb_atok)
{
        uint32_t v;

        CSB_READ(csb_atok, appl_need_kick, v);

        return v;
}
#endif  /* SYNC_KLOOP_POLL */

static inline void
sync_kloop_kring_dump(const char *title, const struct netmap_kring *kring)
{
        nm_prinf("%s, kring %s, hwcur %d, rhead %d, "
                "rcur %d, rtail %d, hwtail %d",
                title, kring->name, kring->nr_hwcur, kring->rhead,
                kring->rcur, kring->rtail, kring->nr_hwtail);
}

/* Arguments for netmap_sync_kloop_tx_ring() and
 * netmap_sync_kloop_rx_ring().
 */
struct sync_kloop_ring_args {
        struct netmap_kring *kring;
        struct nm_csb_atok *csb_atok;
        struct nm_csb_ktoa *csb_ktoa;
#ifdef SYNC_KLOOP_POLL
        struct eventfd_ctx *irq_ctx;
#endif /* SYNC_KLOOP_POLL */
        /* Are we busy waiting rather than using a schedule() loop ? */
        bool busy_wait;
        /* Are we processing in the context of VM exit ? */
        bool direct;
};

static void
netmap_sync_kloop_tx_ring(const struct sync_kloop_ring_args *a)
{
        struct netmap_kring *kring = a->kring;
        struct nm_csb_atok *csb_atok = a->csb_atok;
        struct nm_csb_ktoa *csb_ktoa = a->csb_ktoa;
        /* shadow copy of the netmap_ring */
        struct netmap_ring shadow_ring = {0};
#ifdef SYNC_KLOOP_POLL
        bool more_txspace = false;
#endif /* SYNC_KLOOP_POLL */
        uint32_t num_slots;
        int batch;

        if (unlikely(nm_kr_tryget(kring, 1, NULL))) {
                return;
        }

        num_slots = kring->nkr_num_slots;

        /* Disable application --> kernel notifications. */
        if (!a->direct) {
                csb_ktoa_kick_enable(csb_ktoa, 0);
        }
        /* Copy the application kring pointers from the CSB */
        sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);

        for (;;) {
                batch = shadow_ring.head - kring->nr_hwcur;
                if (batch < 0)
                        batch += num_slots;

#ifdef PTN_TX_BATCH_LIM
                if (batch > PTN_TX_BATCH_LIM(num_slots)) {
                        /* If application moves ahead too fast, let's cut the move so
                         * that we don't exceed our batch limit. */
                        uint32_t head_lim = kring->nr_hwcur + PTN_TX_BATCH_LIM(num_slots);

                        if (head_lim >= num_slots)
                                head_lim -= num_slots;
                        nm_prdis(1, "batch: %d head: %d head_lim: %d", batch, shadow_ring.head,
                                        head_lim);
                        shadow_ring.head = head_lim;
                        batch = PTN_TX_BATCH_LIM(num_slots);
                }
#endif /* PTN_TX_BATCH_LIM */

                if (nm_kr_txspace(kring) <= (num_slots >> 1)) {
                        shadow_ring.flags |= NAF_FORCE_RECLAIM;
                }

                /* Netmap prologue */
                shadow_ring.tail = kring->rtail;
                if (unlikely(nm_txsync_prologue(kring, &shadow_ring) >= num_slots)) {
                        /* Reinit ring and enable notifications. */
                        netmap_ring_reinit(kring);
                        if (!a->busy_wait) {
                                csb_ktoa_kick_enable(csb_ktoa, 1);
                        }
                        break;
                }

                if (unlikely(netmap_debug & NM_DEBUG_TXSYNC)) {
                        sync_kloop_kring_dump("pre txsync", kring);
                }

                if (unlikely(kring->nm_sync(kring, shadow_ring.flags))) {
                        if (!a->busy_wait) {
                                /* Re-enable notifications. */
                                csb_ktoa_kick_enable(csb_ktoa, 1);
                        }
                        nm_prerr("txsync() failed");
                        break;
                }

                /*
                 * Finalize
                 * Copy kernel hwcur and hwtail into the CSB for the application sync(), and
                 * do the nm_sync_finalize.
                 */
                sync_kloop_kernel_write(csb_ktoa, kring->nr_hwcur,
                                kring->nr_hwtail);
                if (kring->rtail != kring->nr_hwtail) {
                        /* Some more room available in the parent adapter. */
                        kring->rtail = kring->nr_hwtail;
#ifdef SYNC_KLOOP_POLL
                        more_txspace = true;
#endif /* SYNC_KLOOP_POLL */
                }

                if (unlikely(netmap_debug & NM_DEBUG_TXSYNC)) {
                        sync_kloop_kring_dump("post txsync", kring);
                }

                /* Interrupt the application if needed. */
#ifdef SYNC_KLOOP_POLL
                if (a->irq_ctx && more_txspace && csb_atok_intr_enabled(csb_atok)) {
                        /* We could disable kernel --> application kicks here,
                         * to avoid spurious interrupts. */
                        eventfd_signal(a->irq_ctx, 1);
                        more_txspace = false;
                }
#endif /* SYNC_KLOOP_POLL */

                /* Read CSB to see if there is more work to do. */
                sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);
                if (shadow_ring.head == kring->rhead) {
                        if (a->busy_wait) {
                                break;
                        }
                        /*
                         * No more packets to transmit. We enable notifications and
                         * go to sleep, waiting for a kick from the application when new
                         * new slots are ready for transmission.
                         */
                        /* Re-enable notifications. */
                        csb_ktoa_kick_enable(csb_ktoa, 1);
                        /* Double check, with store-load memory barrier. */
                        nm_stld_barrier();
                        sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);
                        if (shadow_ring.head != kring->rhead) {
                                /* We won the race condition, there are more packets to
                                 * transmit. Disable notifications and do another cycle */
                                csb_ktoa_kick_enable(csb_ktoa, 0);
                                continue;
                        }
                        break;
                }

                if (nm_kr_txempty(kring)) {
                        /* No more available TX slots. We stop waiting for a notification
                         * from the backend (netmap_tx_irq). */
                        nm_prdis(1, "TX ring");
                        break;
                }
        }

        nm_kr_put(kring);

#ifdef SYNC_KLOOP_POLL
        if (a->irq_ctx && more_txspace && csb_atok_intr_enabled(csb_atok)) {
                eventfd_signal(a->irq_ctx, 1);
        }
#endif /* SYNC_KLOOP_POLL */
}

/* RX cycle without receive any packets */
#define SYNC_LOOP_RX_DRY_CYCLES_MAX     2

static inline int
sync_kloop_norxslots(struct netmap_kring *kring, uint32_t g_head)
{
        return (NM_ACCESS_ONCE(kring->nr_hwtail) == nm_prev(g_head,
                                kring->nkr_num_slots - 1));
}

static void
netmap_sync_kloop_rx_ring(const struct sync_kloop_ring_args *a)
{

        struct netmap_kring *kring = a->kring;
        struct nm_csb_atok *csb_atok = a->csb_atok;
        struct nm_csb_ktoa *csb_ktoa = a->csb_ktoa;
        /* shadow copy of the netmap_ring */
        struct netmap_ring shadow_ring = {0};
        int dry_cycles = 0;
#ifdef SYNC_KLOOP_POLL
        bool some_recvd = false;
#endif /* SYNC_KLOOP_POLL */
        uint32_t num_slots;

        if (unlikely(nm_kr_tryget(kring, 1, NULL))) {
                return;
        }

        num_slots = kring->nkr_num_slots;

        /* Get RX csb_atok and csb_ktoa pointers from the CSB. */
        num_slots = kring->nkr_num_slots;

        /* Disable notifications. */
        if (!a->direct) {
                csb_ktoa_kick_enable(csb_ktoa, 0);
        }
        /* Copy the application kring pointers from the CSB */
        sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);

        for (;;) {
                uint32_t hwtail;

                /* Netmap prologue */
                shadow_ring.tail = kring->rtail;
                if (unlikely(nm_rxsync_prologue(kring, &shadow_ring) >= num_slots)) {
                        /* Reinit ring and enable notifications. */
                        netmap_ring_reinit(kring);
                        if (!a->busy_wait) {
                                csb_ktoa_kick_enable(csb_ktoa, 1);
                        }
                        break;
                }

                if (unlikely(netmap_debug & NM_DEBUG_RXSYNC)) {
                        sync_kloop_kring_dump("pre rxsync", kring);
                }

                if (unlikely(kring->nm_sync(kring, shadow_ring.flags))) {
                        if (!a->busy_wait) {
                                /* Re-enable notifications. */
                                csb_ktoa_kick_enable(csb_ktoa, 1);
                        }
                        nm_prerr("rxsync() failed");
                        break;
                }

                /*
                 * Finalize
                 * Copy kernel hwcur and hwtail into the CSB for the application sync()
                 */
                hwtail = NM_ACCESS_ONCE(kring->nr_hwtail);
                sync_kloop_kernel_write(csb_ktoa, kring->nr_hwcur, hwtail);
                if (kring->rtail != hwtail) {
                        kring->rtail = hwtail;
#ifdef SYNC_KLOOP_POLL
                        some_recvd = true;
#endif /* SYNC_KLOOP_POLL */
                        dry_cycles = 0;
                } else {
                        dry_cycles++;
                }

                if (unlikely(netmap_debug & NM_DEBUG_RXSYNC)) {
                        sync_kloop_kring_dump("post rxsync", kring);
                }

#ifdef SYNC_KLOOP_POLL
                /* Interrupt the application if needed. */
                if (a->irq_ctx && some_recvd && csb_atok_intr_enabled(csb_atok)) {
                        /* We could disable kernel --> application kicks here,
                         * to avoid spurious interrupts. */
                        eventfd_signal(a->irq_ctx, 1);
                        some_recvd = false;
                }
#endif /* SYNC_KLOOP_POLL */

                /* Read CSB to see if there is more work to do. */
                sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);
                if (sync_kloop_norxslots(kring, shadow_ring.head)) {
                        if (a->busy_wait) {
                                break;
                        }
                        /*
                         * No more slots available for reception. We enable notification and
                         * go to sleep, waiting for a kick from the application when new receive
                         * slots are available.
                         */
                        /* Re-enable notifications. */
                        csb_ktoa_kick_enable(csb_ktoa, 1);
                        /* Double check, with store-load memory barrier. */
                        nm_stld_barrier();
                        sync_kloop_kernel_read(csb_atok, &shadow_ring, num_slots);
                        if (!sync_kloop_norxslots(kring, shadow_ring.head)) {
                                /* We won the race condition, more slots are available. Disable
                                 * notifications and do another cycle. */
                                csb_ktoa_kick_enable(csb_ktoa, 0);
                                continue;
                        }
                        break;
                }

                hwtail = NM_ACCESS_ONCE(kring->nr_hwtail);
                if (unlikely(hwtail == kring->rhead ||
                                        dry_cycles >= SYNC_LOOP_RX_DRY_CYCLES_MAX)) {
                        /* No more packets to be read from the backend. We stop and
                         * wait for a notification from the backend (netmap_rx_irq). */
                        nm_prdis(1, "nr_hwtail: %d rhead: %d dry_cycles: %d",
                                        hwtail, kring->rhead, dry_cycles);
                        break;
                }
        }

        nm_kr_put(kring);

#ifdef SYNC_KLOOP_POLL
        /* Interrupt the application if needed. */
        if (a->irq_ctx && some_recvd && csb_atok_intr_enabled(csb_atok)) {
                eventfd_signal(a->irq_ctx, 1);
        }
#endif /* SYNC_KLOOP_POLL */
}

#ifdef SYNC_KLOOP_POLL
struct sync_kloop_poll_ctx;
struct sync_kloop_poll_entry {
        /* Support for receiving notifications from
         * a netmap ring or from the application. */
        struct file *filp;
        wait_queue_t wait;
        wait_queue_head_t *wqh;

        /* Support for sending notifications to the application. */
        struct eventfd_ctx *irq_ctx;
        struct file *irq_filp;

        /* Arguments for the ring processing function. Useful
         * in case of custom wake-up function. */
        struct sync_kloop_ring_args *args;
        struct sync_kloop_poll_ctx *parent;

};

struct sync_kloop_poll_ctx {
        poll_table wait_table;
        unsigned int next_entry;
        int (*next_wake_fun)(wait_queue_t *, unsigned, int, void *);
        unsigned int num_entries;
        unsigned int num_tx_rings;
        unsigned int num_rings;
        /* First num_tx_rings entries are for the TX kicks.
         * Then the RX kicks entries follow. The last two
         * entries are for TX irq, and RX irq. */
        struct sync_kloop_poll_entry entries[0];
};

static void
sync_kloop_poll_table_queue_proc(struct file *file, wait_queue_head_t *wqh,
                                poll_table *pt)
{
        struct sync_kloop_poll_ctx *poll_ctx =
                container_of(pt, struct sync_kloop_poll_ctx, wait_table);
        struct sync_kloop_poll_entry *entry = poll_ctx->entries +
                                                poll_ctx->next_entry;

        BUG_ON(poll_ctx->next_entry >= poll_ctx->num_entries);
        entry->wqh = wqh;
        entry->filp = file;
        /* Use the default wake up function. */
        if (poll_ctx->next_wake_fun == NULL) {
                init_waitqueue_entry(&entry->wait, current);
        } else {
                init_waitqueue_func_entry(&entry->wait,
                    poll_ctx->next_wake_fun);
        }
        add_wait_queue(wqh, &entry->wait);
}

static int
sync_kloop_tx_kick_wake_fun(wait_queue_t *wait, unsigned mode,
    int wake_flags, void *key)
{
        struct sync_kloop_poll_entry *entry =
            container_of(wait, struct sync_kloop_poll_entry, wait);

        netmap_sync_kloop_tx_ring(entry->args);

        return 0;
}

static int
sync_kloop_tx_irq_wake_fun(wait_queue_t *wait, unsigned mode,
    int wake_flags, void *key)
{
        struct sync_kloop_poll_entry *entry =
            container_of(wait, struct sync_kloop_poll_entry, wait);
        struct sync_kloop_poll_ctx *poll_ctx = entry->parent;
        int i;

        for (i = 0; i < poll_ctx->num_tx_rings; i++) {
                struct eventfd_ctx *irq_ctx = poll_ctx->entries[i].irq_ctx;

                if (irq_ctx) {
                        eventfd_signal(irq_ctx, 1);
                }
        }

        return 0;
}

static int
sync_kloop_rx_kick_wake_fun(wait_queue_t *wait, unsigned mode,
    int wake_flags, void *key)
{
        struct sync_kloop_poll_entry *entry =
            container_of(wait, struct sync_kloop_poll_entry, wait);

        netmap_sync_kloop_rx_ring(entry->args);

        return 0;
}

static int
sync_kloop_rx_irq_wake_fun(wait_queue_t *wait, unsigned mode,
    int wake_flags, void *key)
{
        struct sync_kloop_poll_entry *entry =
            container_of(wait, struct sync_kloop_poll_entry, wait);
        struct sync_kloop_poll_ctx *poll_ctx = entry->parent;
        int i;

        for (i = poll_ctx->num_tx_rings; i < poll_ctx->num_rings; i++) {
                struct eventfd_ctx *irq_ctx = poll_ctx->entries[i].irq_ctx;

                if (irq_ctx) {
                        eventfd_signal(irq_ctx, 1);
                }
        }

        return 0;
}
#endif  /* SYNC_KLOOP_POLL */

int
netmap_sync_kloop(struct netmap_priv_d *priv, struct nmreq_header *hdr)
{
        struct nmreq_sync_kloop_start *req =
                (struct nmreq_sync_kloop_start *)(uintptr_t)hdr->nr_body;
        struct nmreq_opt_sync_kloop_eventfds *eventfds_opt = NULL;
#ifdef SYNC_KLOOP_POLL
        struct sync_kloop_poll_ctx *poll_ctx = NULL;
#endif  /* SYNC_KLOOP_POLL */
        int num_rx_rings, num_tx_rings, num_rings;
        struct sync_kloop_ring_args *args = NULL;
        uint32_t sleep_us = req->sleep_us;
        struct nm_csb_atok* csb_atok_base;
        struct nm_csb_ktoa* csb_ktoa_base;
        struct netmap_adapter *na;
        struct nmreq_option *opt;
        bool na_could_sleep = false;
        bool busy_wait = true;
        bool direct_tx = false;
        bool direct_rx = false;
        int err = 0;
        int i;

        if (sleep_us > 1000000) {
                /* We do not accept sleeping for more than a second. */
                return EINVAL;
        }

        if (priv->np_nifp == NULL) {
                return ENXIO;
        }
        mb(); /* make sure following reads are not from cache */

        na = priv->np_na;
        if (!nm_netmap_on(na)) {
                return ENXIO;
        }

        NMG_LOCK();
        /* Make sure the application is working in CSB mode. */
        if (!priv->np_csb_atok_base || !priv->np_csb_ktoa_base) {
                NMG_UNLOCK();
                nm_prerr("sync-kloop on %s requires "
                                "NETMAP_REQ_OPT_CSB option", na->name);
                return EINVAL;
        }

        csb_atok_base = priv->np_csb_atok_base;
        csb_ktoa_base = priv->np_csb_ktoa_base;

        /* Make sure that no kloop is currently running. */
        if (priv->np_kloop_state & NM_SYNC_KLOOP_RUNNING) {
                err = EBUSY;
        }
        priv->np_kloop_state |= NM_SYNC_KLOOP_RUNNING;
        NMG_UNLOCK();
        if (err) {
                return err;
        }

        num_rx_rings = priv->np_qlast[NR_RX] - priv->np_qfirst[NR_RX];
        num_tx_rings = priv->np_qlast[NR_TX] - priv->np_qfirst[NR_TX];
        num_rings = num_tx_rings + num_rx_rings;

        args = nm_os_malloc(num_rings * sizeof(args[0]));
        if (!args) {
                err = ENOMEM;
                goto out;
        }

        /* Prepare the arguments for netmap_sync_kloop_tx_ring()
         * and netmap_sync_kloop_rx_ring(). */
        for (i = 0; i < num_tx_rings; i++) {
                struct sync_kloop_ring_args *a = args + i;

                a->kring = NMR(na, NR_TX)[i + priv->np_qfirst[NR_TX]];
                a->csb_atok = csb_atok_base + i;
                a->csb_ktoa = csb_ktoa_base + i;
                a->busy_wait = busy_wait;
                a->direct = direct_tx;
        }
        for (i = 0; i < num_rx_rings; i++) {
                struct sync_kloop_ring_args *a = args + num_tx_rings + i;

                a->kring = NMR(na, NR_RX)[i + priv->np_qfirst[NR_RX]];
                a->csb_atok = csb_atok_base + num_tx_rings + i;
                a->csb_ktoa = csb_ktoa_base + num_tx_rings + i;
                a->busy_wait = busy_wait;
                a->direct = direct_rx;
        }

        /* Validate notification options. */
        opt = nmreq_getoption(hdr, NETMAP_REQ_OPT_SYNC_KLOOP_MODE);
        if (opt != NULL) {
                struct nmreq_opt_sync_kloop_mode *mode_opt =
                    (struct nmreq_opt_sync_kloop_mode *)opt;

                direct_tx = !!(mode_opt->mode & NM_OPT_SYNC_KLOOP_DIRECT_TX);
                direct_rx = !!(mode_opt->mode & NM_OPT_SYNC_KLOOP_DIRECT_RX);
                if (mode_opt->mode & ~(NM_OPT_SYNC_KLOOP_DIRECT_TX |
                    NM_OPT_SYNC_KLOOP_DIRECT_RX)) {
                        opt->nro_status = err = EINVAL;
                        goto out;
                }
                opt->nro_status = 0;
        }
        opt = nmreq_getoption(hdr, NETMAP_REQ_OPT_SYNC_KLOOP_EVENTFDS);
        if (opt != NULL) {
                if (opt->nro_size != sizeof(*eventfds_opt) +
                        sizeof(eventfds_opt->eventfds[0]) * num_rings) {
                        /* Option size not consistent with the number of
                         * entries. */
                        opt->nro_status = err = EINVAL;
                        goto out;
                }
#ifdef SYNC_KLOOP_POLL
                eventfds_opt = (struct nmreq_opt_sync_kloop_eventfds *)opt;
                opt->nro_status = 0;

                /* Check if some ioeventfd entry is not defined, and force sleep
                 * synchronization in that case. */
                busy_wait = false;
                for (i = 0; i < num_rings; i++) {
                        if (eventfds_opt->eventfds[i].ioeventfd < 0) {
                                busy_wait = true;
                                break;
                        }
                }

                if (busy_wait && (direct_tx || direct_rx)) {
                        /* For direct processing we need all the
                         * ioeventfds to be valid. */
                        opt->nro_status = err = EINVAL;
                        goto out;
                }

                /* We need 2 poll entries for TX and RX notifications coming
                 * from the netmap adapter, plus one entries per ring for the
                 * notifications coming from the application. */
                poll_ctx = nm_os_malloc(sizeof(*poll_ctx) +
                                (num_rings + 2) * sizeof(poll_ctx->entries[0]));
                init_poll_funcptr(&poll_ctx->wait_table,
                                        sync_kloop_poll_table_queue_proc);
                poll_ctx->num_entries = 2 + num_rings;
                poll_ctx->num_tx_rings = num_tx_rings;
                poll_ctx->num_rings = num_rings;
                poll_ctx->next_entry = 0;
                poll_ctx->next_wake_fun = NULL;

                if (direct_tx && (na->na_flags & NAF_BDG_MAYSLEEP)) {
                        /* In direct mode, VALE txsync is called from
                         * wake-up context, where it is not possible
                         * to sleep.
                         */
                        na->na_flags &= ~NAF_BDG_MAYSLEEP;
                        na_could_sleep = true;
                }

                for (i = 0; i < num_rings + 2; i++) {
                        poll_ctx->entries[i].args = args + i;
                        poll_ctx->entries[i].parent = poll_ctx;
                }

                /* Poll for notifications coming from the applications through
                 * eventfds. */
                for (i = 0; i < num_rings; i++, poll_ctx->next_entry++) {
                        struct eventfd_ctx *irq = NULL;
                        struct file *filp = NULL;
                        unsigned long mask;
                        bool tx_ring = (i < num_tx_rings);

                        if (eventfds_opt->eventfds[i].irqfd >= 0) {
                                filp = eventfd_fget(
                                    eventfds_opt->eventfds[i].irqfd);
                                if (IS_ERR(filp)) {
                                        err = PTR_ERR(filp);
                                        goto out;
                                }
                                irq = eventfd_ctx_fileget(filp);
                                if (IS_ERR(irq)) {
                                        err = PTR_ERR(irq);
                                        goto out;
                                }
                        }
                        poll_ctx->entries[i].irq_filp = filp;
                        poll_ctx->entries[i].irq_ctx = irq;
                        poll_ctx->entries[i].args->busy_wait = busy_wait;
                        /* Don't let netmap_sync_kloop_*x_ring() use
                         * IRQs in direct mode. */
                        poll_ctx->entries[i].args->irq_ctx =
                            ((tx_ring && direct_tx) ||
                            (!tx_ring && direct_rx)) ? NULL :
                            poll_ctx->entries[i].irq_ctx;
                        poll_ctx->entries[i].args->direct =
                            (tx_ring ? direct_tx : direct_rx);

                        if (!busy_wait) {
                                filp = eventfd_fget(
                                    eventfds_opt->eventfds[i].ioeventfd);
                                if (IS_ERR(filp)) {
                                        err = PTR_ERR(filp);
                                        goto out;
                                }
                                if (tx_ring && direct_tx) {
                                        /* Override the wake up function
                                         * so that it can directly call
                                         * netmap_sync_kloop_tx_ring().
                                         */
                                        poll_ctx->next_wake_fun =
                                            sync_kloop_tx_kick_wake_fun;
                                } else if (!tx_ring && direct_rx) {
                                        /* Same for direct RX. */
                                        poll_ctx->next_wake_fun =
                                            sync_kloop_rx_kick_wake_fun;
                                } else {
                                        poll_ctx->next_wake_fun = NULL;
                                }
                                mask = filp->f_op->poll(filp,
                                    &poll_ctx->wait_table);
                                if (mask & POLLERR) {
                                        err = EINVAL;
                                        goto out;
                                }
                        }
                }

                /* Poll for notifications coming from the netmap rings bound to
                 * this file descriptor. */
                if (!busy_wait) {
                        NMG_LOCK();
                        /* In direct mode, override the wake up function so
                         * that it can forward the netmap_tx_irq() to the
                         * guest. */
                        poll_ctx->next_wake_fun = direct_tx ?
                            sync_kloop_tx_irq_wake_fun : NULL;
                        poll_wait(priv->np_filp, priv->np_si[NR_TX],
                            &poll_ctx->wait_table);
                        poll_ctx->next_entry++;

                        poll_ctx->next_wake_fun = direct_rx ?
                            sync_kloop_rx_irq_wake_fun : NULL;
                        poll_wait(priv->np_filp, priv->np_si[NR_RX],
                            &poll_ctx->wait_table);
                        poll_ctx->next_entry++;
                        NMG_UNLOCK();
                }
#else   /* SYNC_KLOOP_POLL */
                opt->nro_status = EOPNOTSUPP;
                goto out;
#endif  /* SYNC_KLOOP_POLL */
        }

        nm_prinf("kloop busy_wait %u, direct_tx %u, direct_rx %u, "
            "na_could_sleep %u", busy_wait, direct_tx, direct_rx,
            na_could_sleep);

        /* Main loop. */
        for (;;) {
                if (unlikely(NM_ACCESS_ONCE(priv->np_kloop_state) & NM_SYNC_KLOOP_STOPPING)) {
                        break;
                }

#ifdef SYNC_KLOOP_POLL
                if (!busy_wait) {
                        /* It is important to set the task state as
                         * interruptible before processing any TX/RX ring,
                         * so that if a notification on ring Y comes after
                         * we have processed ring Y, but before we call
                         * schedule(), we don't miss it. This is true because
                         * the wake up function will change the task state,
                         * and therefore the schedule_timeout() call below
                         * will observe the change).
                         */
                        set_current_state(TASK_INTERRUPTIBLE);
                }
#endif  /* SYNC_KLOOP_POLL */

                /* Process all the TX rings bound to this file descriptor. */
                for (i = 0; !direct_tx && i < num_tx_rings; i++) {
                        struct sync_kloop_ring_args *a = args + i;
                        netmap_sync_kloop_tx_ring(a);
                }

                /* Process all the RX rings bound to this file descriptor. */
                for (i = 0; !direct_rx && i < num_rx_rings; i++) {
                        struct sync_kloop_ring_args *a = args + num_tx_rings + i;
                        netmap_sync_kloop_rx_ring(a);
                }

                if (busy_wait) {
                        /* Default synchronization method: sleep for a while. */
                        usleep_range(sleep_us, sleep_us);
                }
#ifdef SYNC_KLOOP_POLL
                else {
                        /* Yield to the scheduler waiting for a notification
                         * to come either from netmap or the application. */
                        schedule_timeout(msecs_to_jiffies(3000));
                }
#endif /* SYNC_KLOOP_POLL */
        }
out:
#ifdef SYNC_KLOOP_POLL
        if (poll_ctx) {
                /* Stop polling from netmap and the eventfds, and deallocate
                 * the poll context. */
                if (!busy_wait) {
                        __set_current_state(TASK_RUNNING);
                }
                for (i = 0; i < poll_ctx->next_entry; i++) {
                        struct sync_kloop_poll_entry *entry =
                                                poll_ctx->entries + i;

                        if (entry->wqh)
                                remove_wait_queue(entry->wqh, &entry->wait);
                        /* We did not get a reference to the eventfds, but
                         * don't do that on netmap file descriptors (since
                         * a reference was not taken. */
                        if (entry->filp && entry->filp != priv->np_filp)
                                fput(entry->filp);
                        if (entry->irq_ctx)
                                eventfd_ctx_put(entry->irq_ctx);
                        if (entry->irq_filp)
                                fput(entry->irq_filp);
                }
                nm_os_free(poll_ctx);
                poll_ctx = NULL;
        }
#endif /* SYNC_KLOOP_POLL */

        if (args) {
                nm_os_free(args);
                args = NULL;
        }

        /* Reset the kloop state. */
        NMG_LOCK();
        priv->np_kloop_state = 0;
        if (na_could_sleep) {
                na->na_flags |= NAF_BDG_MAYSLEEP;
        }
        NMG_UNLOCK();

        return err;
}

int
netmap_sync_kloop_stop(struct netmap_priv_d *priv)
{
        struct netmap_adapter *na;
        bool running = true;
        int err = 0;

        if (priv->np_nifp == NULL) {
                return ENXIO;
        }
        mb(); /* make sure following reads are not from cache */

        na = priv->np_na;
        if (!nm_netmap_on(na)) {
                return ENXIO;
        }

        /* Set the kloop stopping flag. */
        NMG_LOCK();
        priv->np_kloop_state |= NM_SYNC_KLOOP_STOPPING;
        NMG_UNLOCK();

        /* Send a notification to the kloop, in case it is blocked in
         * schedule_timeout(). We can use either RX or TX, because the
         * kloop is waiting on both. */
        nm_os_selwakeup(priv->np_si[NR_RX]);

        /* Wait for the kloop to actually terminate. */
        while (running) {
                usleep_range(1000, 1500);
                NMG_LOCK();
                running = (NM_ACCESS_ONCE(priv->np_kloop_state)
                                & NM_SYNC_KLOOP_RUNNING);
                NMG_UNLOCK();
        }

        return err;
}

#ifdef WITH_PTNETMAP
/*
 * Guest ptnetmap txsync()/rxsync() routines, used in ptnet device drivers.
 * These routines are reused across the different operating systems supported
 * by netmap.
 */

/*
 * Reconcile host and guest views of the transmit ring.
 *
 * Guest user wants to transmit packets up to the one before ring->head,
 * and guest kernel knows tx_ring->hwcur is the first packet unsent
 * by the host kernel.
 *
 * We push out as many packets as possible, and possibly
 * reclaim buffers from previously completed transmission.
 *
 * Notifications from the host are enabled only if the user guest would
 * block (no space in the ring).
 */
bool
netmap_pt_guest_txsync(struct nm_csb_atok *atok, struct nm_csb_ktoa *ktoa,
                        struct netmap_kring *kring, int flags)
{
        bool notify = false;

        /* Disable notifications */
        atok->appl_need_kick = 0;

        /*
         * First part: tell the host to process the new packets,
         * updating the CSB.
         */
        kring->nr_hwcur = ktoa->hwcur;
        nm_sync_kloop_appl_write(atok, kring->rcur, kring->rhead);

        /* Ask for a kick from a guest to the host if needed. */
        if (((kring->rhead != kring->nr_hwcur || nm_kr_wouldblock(kring))
                && NM_ACCESS_ONCE(ktoa->kern_need_kick)) ||
                        (flags & NAF_FORCE_RECLAIM)) {
                atok->sync_flags = flags;
                notify = true;
        }

        /*
         * Second part: reclaim buffers for completed transmissions.
         */
        if (nm_kr_wouldblock(kring) || (flags & NAF_FORCE_RECLAIM)) {
                nm_sync_kloop_appl_read(ktoa, &kring->nr_hwtail,
                                        &kring->nr_hwcur);
        }

        /*
         * No more room in the ring for new transmissions. The user thread will
         * go to sleep and we need to be notified by the host when more free
         * space is available.
         */
        if (nm_kr_wouldblock(kring) && !(kring->nr_kflags & NKR_NOINTR)) {
                /* Re-enable notifications. */
                atok->appl_need_kick = 1;
                /* Double check, with store-load memory barrier. */
                nm_stld_barrier();
                nm_sync_kloop_appl_read(ktoa, &kring->nr_hwtail,
                                        &kring->nr_hwcur);
                /* If there is new free space, disable notifications */
                if (unlikely(!nm_kr_wouldblock(kring))) {
                        atok->appl_need_kick = 0;
                }
        }

        nm_prdis(1, "%s CSB(head:%u cur:%u hwtail:%u) KRING(head:%u cur:%u tail:%u)",
                kring->name, atok->head, atok->cur, ktoa->hwtail,
                kring->rhead, kring->rcur, kring->nr_hwtail);

        return notify;
}

/*
 * Reconcile host and guest view of the receive ring.
 *
 * Update hwcur/hwtail from host (reading from CSB).
 *
 * If guest user has released buffers up to the one before ring->head, we
 * also give them to the host.
 *
 * Notifications from the host are enabled only if the user guest would
 * block (no more completed slots in the ring).
 */
bool
netmap_pt_guest_rxsync(struct nm_csb_atok *atok, struct nm_csb_ktoa *ktoa,
                        struct netmap_kring *kring, int flags)
{
        bool notify = false;

        /* Disable notifications */
        atok->appl_need_kick = 0;

        /*
         * First part: import newly received packets, by updating the kring
         * hwtail to the hwtail known from the host (read from the CSB).
         * This also updates the kring hwcur.
         */
        nm_sync_kloop_appl_read(ktoa, &kring->nr_hwtail, &kring->nr_hwcur);
        kring->nr_kflags &= ~NKR_PENDINTR;

        /*
         * Second part: tell the host about the slots that guest user has
         * released, by updating cur and head in the CSB.
         */
        if (kring->rhead != kring->nr_hwcur) {
                nm_sync_kloop_appl_write(atok, kring->rcur, kring->rhead);
        }

        /*
         * No more completed RX slots. The user thread will go to sleep and
         * we need to be notified by the host when more RX slots have been
         * completed.
         */
        if (nm_kr_wouldblock(kring) && !(kring->nr_kflags & NKR_NOINTR)) {
                /* Re-enable notifications. */
                atok->appl_need_kick = 1;
                /* Double check, with store-load memory barrier. */
                nm_stld_barrier();
                nm_sync_kloop_appl_read(ktoa, &kring->nr_hwtail,
                                        &kring->nr_hwcur);
                /* If there are new slots, disable notifications. */
                if (!nm_kr_wouldblock(kring)) {
                        atok->appl_need_kick = 0;
                }
        }

        /* Ask for a kick from the guest to the host if needed. */
        if ((kring->rhead != kring->nr_hwcur || nm_kr_wouldblock(kring))
                && NM_ACCESS_ONCE(ktoa->kern_need_kick)) {
                atok->sync_flags = flags;
                notify = true;
        }

        nm_prdis(1, "%s CSB(head:%u cur:%u hwtail:%u) KRING(head:%u cur:%u tail:%u)",
                kring->name, atok->head, atok->cur, ktoa->hwtail,
                kring->rhead, kring->rcur, kring->nr_hwtail);

        return notify;
}

/*
 * Callbacks for ptnet drivers: nm_krings_create, nm_krings_delete, nm_dtor.
 */
int
ptnet_nm_krings_create(struct netmap_adapter *na)
{
        struct netmap_pt_guest_adapter *ptna =
                        (struct netmap_pt_guest_adapter *)na; /* Upcast. */
        struct netmap_adapter *na_nm = &ptna->hwup.up;
        struct netmap_adapter *na_dr = &ptna->dr.up;
        int ret;

        if (ptna->backend_users) {
                return 0;
        }

        /* Create krings on the public netmap adapter. */
        ret = netmap_hw_krings_create(na_nm);
        if (ret) {
                return ret;
        }

        /* Copy krings into the netmap adapter private to the driver. */
        na_dr->tx_rings = na_nm->tx_rings;
        na_dr->rx_rings = na_nm->rx_rings;

        return 0;
}

void
ptnet_nm_krings_delete(struct netmap_adapter *na)
{
        struct netmap_pt_guest_adapter *ptna =
                        (struct netmap_pt_guest_adapter *)na; /* Upcast. */
        struct netmap_adapter *na_nm = &ptna->hwup.up;
        struct netmap_adapter *na_dr = &ptna->dr.up;

        if (ptna->backend_users) {
                return;
        }

        na_dr->tx_rings = NULL;
        na_dr->rx_rings = NULL;

        netmap_hw_krings_delete(na_nm);
}

void
ptnet_nm_dtor(struct netmap_adapter *na)
{
        struct netmap_pt_guest_adapter *ptna =
                        (struct netmap_pt_guest_adapter *)na;

        netmap_mem_put(ptna->dr.up.nm_mem);
        memset(&ptna->dr, 0, sizeof(ptna->dr));
        netmap_mem_pt_guest_ifp_del(na->nm_mem, na->ifp);
}

int
netmap_pt_guest_attach(struct netmap_adapter *arg,
                       unsigned int nifp_offset, unsigned int memid)
{
        struct netmap_pt_guest_adapter *ptna;
        if_t ifp = arg ? arg->ifp : NULL;
        int error;

        /* get allocator */
        arg->nm_mem = netmap_mem_pt_guest_new(ifp, nifp_offset, memid);
        if (arg->nm_mem == NULL)
                return ENOMEM;
        arg->na_flags |= NAF_MEM_OWNER;
        error = netmap_attach_ext(arg, sizeof(struct netmap_pt_guest_adapter), 1);
        if (error)
                return error;

        /* get the netmap_pt_guest_adapter */
        ptna = (struct netmap_pt_guest_adapter *) NA(ifp);

        /* Initialize a separate pass-through netmap adapter that is going to
         * be used by the ptnet driver only, and so never exposed to netmap
         * applications. We only need a subset of the available fields. */
        memset(&ptna->dr, 0, sizeof(ptna->dr));
        ptna->dr.up.ifp = ifp;
        ptna->dr.up.nm_mem = netmap_mem_get(ptna->hwup.up.nm_mem);
        ptna->dr.up.nm_config = ptna->hwup.up.nm_config;

        ptna->backend_users = 0;

        return 0;
}

#endif /* WITH_PTNETMAP */