Commit 9b02e161 authored by Wei Wang's avatar Wei Wang Committed by Michael S. Tsirkin
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virtio-net: enable configurable tx queue size 



This patch enables the virtio-net tx queue size to be configurable
between 256 (the default queue size) and 1024 by the user when the
vhost-user backend is used.

Currently, the maximum tx queue size for other backends is 512 due
to the following limitations:
- QEMU backend: the QEMU backend implementation in some cases may
send 1024+1 iovs to writev.
- Vhost_net backend: there are possibilities that the guest sends
a vring_desc of memory which crosses a MemoryRegion thereby
generating more than 1024 iovs after translation from guest-physical
address in the backend.

Signed-off-by: default avatarWei Wang <wei.w.wang@intel.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent fd479c60

hw/net/virtio-net.c

+30 −2
Original line number Diff line number Diff line
@@ -34,8 +34,11 @@ 


/* previously fixed value */

#define VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE 256

#define VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE 256



/* for now, only allow larger queues; with virtio-1, guest can downsize */

#define VIRTIO_NET_RX_QUEUE_MIN_SIZE VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE

#define VIRTIO_NET_TX_QUEUE_MIN_SIZE VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE



/*

 * Calculate the number of bytes up to and including the given 'field' of
@@ -1508,15 +1511,18 @@ static void virtio_net_add_queue(VirtIONet *n, int index) 


    n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_queue_size,

                                           virtio_net_handle_rx);



    if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) {

        n->vqs[index].tx_vq =

            virtio_add_queue(vdev, 256, virtio_net_handle_tx_timer);

            virtio_add_queue(vdev, n->net_conf.tx_queue_size,

                             virtio_net_handle_tx_timer);

        n->vqs[index].tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,

                                              virtio_net_tx_timer,

                                              &n->vqs[index]);

    } else {

        n->vqs[index].tx_vq =

            virtio_add_queue(vdev, 256, virtio_net_handle_tx_bh);

            virtio_add_queue(vdev, n->net_conf.tx_queue_size,

                             virtio_net_handle_tx_bh);

        n->vqs[index].tx_bh = qemu_bh_new(virtio_net_tx_bh, &n->vqs[index]);

    }
@@ -1927,6 +1933,17 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) 
        return;

    }



    if (n->net_conf.tx_queue_size < VIRTIO_NET_TX_QUEUE_MIN_SIZE ||

        n->net_conf.tx_queue_size > VIRTQUEUE_MAX_SIZE ||

        !is_power_of_2(n->net_conf.tx_queue_size)) {

        error_setg(errp, "Invalid tx_queue_size (= %" PRIu16 "), "

                   "must be a power of 2 between %d and %d",

                   n->net_conf.tx_queue_size, VIRTIO_NET_TX_QUEUE_MIN_SIZE,

                   VIRTQUEUE_MAX_SIZE);

        virtio_cleanup(vdev);

        return;

    }



    n->max_queues = MAX(n->nic_conf.peers.queues, 1);

    if (n->max_queues * 2 + 1 > VIRTIO_QUEUE_MAX) {

        error_setg(errp, "Invalid number of queues (= %" PRIu32 "), "
@@ -1947,6 +1964,15 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) 
        error_report("Defaulting to \"bh\"");

    }



    /*

     * Currently, backends other than vhost-user don't support 1024 queue

     * size.

     */

    if (n->net_conf.tx_queue_size == VIRTQUEUE_MAX_SIZE &&

        n->nic_conf.peers.ncs[0]->info->type != NET_CLIENT_DRIVER_VHOST_USER) {

        n->net_conf.tx_queue_size = VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;

    }



    for (i = 0; i < n->max_queues; i++) {

        virtio_net_add_queue(n, i);

    }
@@ -2106,6 +2132,8 @@ static Property virtio_net_properties[] = { 
    DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx),

    DEFINE_PROP_UINT16("rx_queue_size", VirtIONet, net_conf.rx_queue_size,

                       VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE),

    DEFINE_PROP_UINT16("tx_queue_size", VirtIONet, net_conf.tx_queue_size,

                       VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE),

    DEFINE_PROP_UINT16("host_mtu", VirtIONet, net_conf.mtu, 0),

    DEFINE_PROP_BOOL("x-mtu-bypass-backend", VirtIONet, mtu_bypass_backend,

                     true),

include/hw/virtio/virtio-net.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ typedef struct virtio_net_conf 
    int32_t txburst;

    char *tx;

    uint16_t rx_queue_size;

    uint16_t tx_queue_size;

    uint16_t mtu;

} virtio_net_conf;