examples/vhost/virtio_net.c

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2017 Intel Corporation
 */

#include <stdint.h>
#include <stdbool.h>
#include <linux/virtio_net.h>

#include <rte_mbuf.h>
#include <rte_memcpy.h>
#include <rte_vhost.h>

#include "main.h"

/*
 * A very simple vhost-user net driver implementation, without
 * any extra features being enabled, such as TSO and mrg-Rx.
 */

void
vs_vhost_net_setup(struct vhost_dev *dev)
{
    uint16_t i;
    int vid = dev->vid;
    struct vhost_queue *queue;

    RTE_LOG(INFO, VHOST_CONFIG,
        "setting builtin vhost-user net driver\n");

    rte_vhost_get_negotiated_features(vid, &dev->features);
    if (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF))
        dev->hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
    else
        dev->hdr_len = sizeof(struct virtio_net_hdr);

    rte_vhost_get_mem_table(vid, &dev->mem);

    dev->nr_vrings = rte_vhost_get_vring_num(vid);
    for (i = 0; i < dev->nr_vrings; i++) {
        queue = &dev->queues[i];

        queue->last_used_idx  = 0;
        queue->last_avail_idx = 0;
        rte_vhost_get_vhost_vring(vid, i, &queue->vr);
    }
}

void
vs_vhost_net_remove(struct vhost_dev *dev)
{
    free(dev->mem);
}

static __rte_always_inline int
enqueue_pkt(struct vhost_dev *dev, struct rte_vhost_vring *vr,
        struct rte_mbuf *m, uint16_t desc_idx)
{
    uint32_t desc_avail, desc_offset;
    uint64_t desc_chunck_len;
    uint32_t mbuf_avail, mbuf_offset;
    uint32_t cpy_len;
    struct vring_desc *desc;
    uint64_t desc_addr, desc_gaddr;
    struct virtio_net_hdr virtio_hdr = {0, 0, 0, 0, 0, 0};
    /* A counter to avoid desc dead loop chain */
    uint16_t nr_desc = 1;

    desc = &vr->desc[desc_idx];
    desc_chunck_len = desc->len;
    desc_gaddr = desc->addr;
    desc_addr = rte_vhost_va_from_guest_pa(
            dev->mem, desc_gaddr, &desc_chunck_len);
    /*
     * Checking of 'desc_addr' placed outside of 'unlikely' macro to avoid
     * performance issue with some versions of gcc (4.8.4 and 5.3.0) which
     * otherwise stores offset on the stack instead of in a register.
     */
    if (unlikely(desc->len < dev->hdr_len) || !desc_addr)
        return -1;

    rte_prefetch0((void *)(uintptr_t)desc_addr);

    /* write virtio-net header */
    if (likely(desc_chunck_len >= dev->hdr_len)) {
        *(struct virtio_net_hdr *)(uintptr_t)desc_addr = virtio_hdr;
        desc_offset = dev->hdr_len;
    } else {
        uint64_t len;
        uint64_t remain = dev->hdr_len;
        uint64_t src = (uint64_t)(uintptr_t)&virtio_hdr, dst;
        uint64_t guest_addr = desc_gaddr;

        while (remain) {
            len = remain;
            dst = rte_vhost_va_from_guest_pa(dev->mem,
                    guest_addr, &len);
            if (unlikely(!dst || !len))
                return -1;

            rte_memcpy((void *)(uintptr_t)dst,
                    (void *)(uintptr_t)src,
                    len);

            remain -= len;
            guest_addr += len;
            src += len;
        }

        desc_chunck_len = desc->len - dev->hdr_len;
        desc_gaddr += dev->hdr_len;
        desc_addr = rte_vhost_va_from_guest_pa(
                dev->mem, desc_gaddr,
                &desc_chunck_len);
        if (unlikely(!desc_addr))
            return -1;

        desc_offset = 0;
    }

    desc_avail  = desc->len - dev->hdr_len;

    mbuf_avail  = rte_pktmbuf_data_len(m);
    mbuf_offset = 0;
    while (mbuf_avail != 0 || m->next != NULL) {
        /* done with current mbuf, fetch next */
        if (mbuf_avail == 0) {
            m = m->next;

            mbuf_offset = 0;
            mbuf_avail  = rte_pktmbuf_data_len(m);
        }

        /* done with current desc buf, fetch next */
        if (desc_avail == 0) {
            if ((desc->flags & VRING_DESC_F_NEXT) == 0) {
                /* Room in vring buffer is not enough */
                return -1;
            }
            if (unlikely(desc->next >= vr->size ||
                     ++nr_desc > vr->size))
                return -1;

            desc = &vr->desc[desc->next];
            desc_chunck_len = desc->len;
            desc_gaddr = desc->addr;
            desc_addr = rte_vhost_va_from_guest_pa(
                    dev->mem, desc_gaddr, &desc_chunck_len);
            if (unlikely(!desc_addr))
                return -1;

            desc_offset = 0;
            desc_avail  = desc->len;
        } else if (unlikely(desc_chunck_len == 0)) {
            desc_chunck_len = desc_avail;
            desc_gaddr += desc_offset;
            desc_addr = rte_vhost_va_from_guest_pa(dev->mem,
                    desc_gaddr,
                    &desc_chunck_len);
            if (unlikely(!desc_addr))
                return -1;

            desc_offset = 0;
        }

        cpy_len = RTE_MIN(desc_chunck_len, mbuf_avail);
        rte_memcpy((void *)((uintptr_t)(desc_addr + desc_offset)),
            rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
            cpy_len);

        mbuf_avail  -= cpy_len;
        mbuf_offset += cpy_len;
        desc_avail  -= cpy_len;
        desc_offset += cpy_len;
        desc_chunck_len -= cpy_len;
    }

    return 0;
}

uint16_t
vs_enqueue_pkts(struct vhost_dev *dev, uint16_t queue_id,
        struct rte_mbuf **pkts, uint32_t count)
{
    struct vhost_queue *queue;
    struct rte_vhost_vring *vr;
    uint16_t avail_idx, free_entries, start_idx;
    uint16_t desc_indexes[MAX_PKT_BURST];
    uint16_t used_idx;
    uint32_t i;

    queue = &dev->queues[queue_id];
    vr    = &queue->vr;

    avail_idx = __atomic_load_n(&vr->avail->idx, __ATOMIC_ACQUIRE);
    start_idx = queue->last_used_idx;
    free_entries = avail_idx - start_idx;
    count = RTE_MIN(count, free_entries);
    count = RTE_MIN(count, (uint32_t)MAX_PKT_BURST);
    if (count == 0)
        return 0;

    /* Retrieve all of the desc indexes first to avoid caching issues. */
    rte_prefetch0(&vr->avail->ring[start_idx & (vr->size - 1)]);
    for (i = 0; i < count; i++) {
        used_idx = (start_idx + i) & (vr->size - 1);
        desc_indexes[i] = vr->avail->ring[used_idx];
        vr->used->ring[used_idx].id = desc_indexes[i];
        vr->used->ring[used_idx].len = pkts[i]->pkt_len +
                           dev->hdr_len;
    }

    rte_prefetch0(&vr->desc[desc_indexes[0]]);
    for (i = 0; i < count; i++) {
        uint16_t desc_idx = desc_indexes[i];
        int err;

        err = enqueue_pkt(dev, vr, pkts[i], desc_idx);
        if (unlikely(err)) {
            used_idx = (start_idx + i) & (vr->size - 1);
            vr->used->ring[used_idx].len = dev->hdr_len;
        }

        if (i + 1 < count)
            rte_prefetch0(&vr->desc[desc_indexes[i+1]]);
    }

    __atomic_add_fetch(&vr->used->idx, count, __ATOMIC_RELEASE);
    queue->last_used_idx += count;

    rte_vhost_vring_call(dev->vid, queue_id);

    return count;
}

static __rte_always_inline int
dequeue_pkt(struct vhost_dev *dev, struct rte_vhost_vring *vr,
        struct rte_mbuf *m, uint16_t desc_idx,
        struct rte_mempool *mbuf_pool)
{
    struct vring_desc *desc;
    uint64_t desc_addr, desc_gaddr;
    uint32_t desc_avail, desc_offset;
    uint64_t desc_chunck_len;
    uint32_t mbuf_avail, mbuf_offset;
    uint32_t cpy_len;
    struct rte_mbuf *cur = m, *prev = m;
    /* A counter to avoid desc dead loop chain */
    uint32_t nr_desc = 1;

    desc = &vr->desc[desc_idx];
    if (unlikely((desc->len < dev->hdr_len)) ||
            (desc->flags & VRING_DESC_F_INDIRECT))
        return -1;

    desc_chunck_len = desc->len;
    desc_gaddr = desc->addr;
    desc_addr = rte_vhost_va_from_guest_pa(
            dev->mem, desc_gaddr, &desc_chunck_len);
    if (unlikely(!desc_addr))
        return -1;

    /*
     * We don't support ANY_LAYOUT, neither VERSION_1, meaning
     * a Tx packet from guest must have 2 desc buffers at least:
     * the first for storing the header and the others for
     * storing the data.
     *
     * And since we don't support TSO, we could simply skip the
     * header.
     */
    desc = &vr->desc[desc->next];
    desc_chunck_len = desc->len;
    desc_gaddr = desc->addr;
    desc_addr = rte_vhost_va_from_guest_pa(
            dev->mem, desc_gaddr, &desc_chunck_len);
    if (unlikely(!desc_addr))
        return -1;
    rte_prefetch0((void *)(uintptr_t)desc_addr);

    desc_offset = 0;
    desc_avail  = desc->len;
    nr_desc    += 1;

    mbuf_offset = 0;
    mbuf_avail  = m->buf_len - RTE_PKTMBUF_HEADROOM;
    while (1) {
        cpy_len = RTE_MIN(desc_chunck_len, mbuf_avail);
        rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *,
                           mbuf_offset),
            (void *)((uintptr_t)(desc_addr + desc_offset)),
            cpy_len);

        mbuf_avail  -= cpy_len;
        mbuf_offset += cpy_len;
        desc_avail  -= cpy_len;
        desc_offset += cpy_len;
        desc_chunck_len -= cpy_len;

        /* This desc reaches to its end, get the next one */
        if (desc_avail == 0) {
            if ((desc->flags & VRING_DESC_F_NEXT) == 0)
                break;

            if (unlikely(desc->next >= vr->size ||
                     ++nr_desc > vr->size))
                return -1;
            desc = &vr->desc[desc->next];

            desc_chunck_len = desc->len;
            desc_gaddr = desc->addr;
            desc_addr = rte_vhost_va_from_guest_pa(
                    dev->mem, desc_gaddr, &desc_chunck_len);
            if (unlikely(!desc_addr))
                return -1;
            rte_prefetch0((void *)(uintptr_t)desc_addr);

            desc_offset = 0;
            desc_avail  = desc->len;
        } else if (unlikely(desc_chunck_len == 0)) {
            desc_chunck_len = desc_avail;
            desc_gaddr += desc_offset;
            desc_addr = rte_vhost_va_from_guest_pa(dev->mem,
                    desc_gaddr,
                    &desc_chunck_len);
            if (unlikely(!desc_addr))
                return -1;

            desc_offset = 0;
        }

        /*
         * This mbuf reaches to its end, get a new one
         * to hold more data.
         */
        if (mbuf_avail == 0) {
            cur = rte_pktmbuf_alloc(mbuf_pool);
            if (unlikely(cur == NULL)) {
                RTE_LOG(ERR, VHOST_DATA, "Failed to "
                    "allocate memory for mbuf.\n");
                return -1;
            }

            prev->next = cur;
            prev->data_len = mbuf_offset;
            m->nb_segs += 1;
            m->pkt_len += mbuf_offset;
            prev = cur;

            mbuf_offset = 0;
            mbuf_avail  = cur->buf_len - RTE_PKTMBUF_HEADROOM;
        }
    }

    prev->data_len = mbuf_offset;
    m->pkt_len    += mbuf_offset;

    return 0;
}

uint16_t
vs_dequeue_pkts(struct vhost_dev *dev, uint16_t queue_id,
    struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
{
    struct vhost_queue *queue;
    struct rte_vhost_vring *vr;
    uint32_t desc_indexes[MAX_PKT_BURST];
    uint32_t used_idx;
    uint32_t i = 0;
    uint16_t free_entries;
    uint16_t avail_idx;

    queue = &dev->queues[queue_id];
    vr    = &queue->vr;

    free_entries = __atomic_load_n(&vr->avail->idx, __ATOMIC_ACQUIRE) -
            queue->last_avail_idx;
    if (free_entries == 0)
        return 0;

    /* Prefetch available and used ring */
    avail_idx = queue->last_avail_idx & (vr->size - 1);
    used_idx  = queue->last_used_idx  & (vr->size - 1);
    rte_prefetch0(&vr->avail->ring[avail_idx]);
    rte_prefetch0(&vr->used->ring[used_idx]);

    count = RTE_MIN(count, MAX_PKT_BURST);
    count = RTE_MIN(count, free_entries);

    if (unlikely(count == 0))
        return 0;

    /*
     * Retrieve all of the head indexes first and pre-update used entries
     * to avoid caching issues.
     */
    for (i = 0; i < count; i++) {
        avail_idx = (queue->last_avail_idx + i) & (vr->size - 1);
        used_idx  = (queue->last_used_idx  + i) & (vr->size - 1);
        desc_indexes[i] = vr->avail->ring[avail_idx];

        vr->used->ring[used_idx].id  = desc_indexes[i];
        vr->used->ring[used_idx].len = 0;
    }

    /* Prefetch descriptor index. */
    rte_prefetch0(&vr->desc[desc_indexes[0]]);
    for (i = 0; i < count; i++) {
        int err;

        if (likely(i + 1 < count))
            rte_prefetch0(&vr->desc[desc_indexes[i + 1]]);

        pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
        if (unlikely(pkts[i] == NULL)) {
            RTE_LOG(ERR, VHOST_DATA,
                "Failed to allocate memory for mbuf.\n");
            break;
        }

        err = dequeue_pkt(dev, vr, pkts[i], desc_indexes[i], mbuf_pool);
        if (unlikely(err)) {
            rte_pktmbuf_free(pkts[i]);
            break;
        }

    }

    queue->last_avail_idx += i;
    queue->last_used_idx += i;

    __atomic_add_fetch(&vr->used->idx, i, __ATOMIC_ACQ_REL);

    rte_vhost_vring_call(dev->vid, queue_id);

    return i;
}