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 = *((volatile uint16_t *)&vr->avail->idx);
        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]]);
        }

        rte_smp_wmb();

        *(volatile uint16_t *)&vr->used->idx += count;
        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 = *((volatile uint16_t *)&vr->avail->idx) -
                        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;
        rte_smp_wmb();
        rte_smp_rmb();

        vr->used->idx += i;

        rte_vhost_vring_call(dev->vid, queue_id);

        return i;
}