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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: Wei Wang <wei.w.wang@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Wei Wang 2017-06-28 10:37:59 +08:00 committed by Michael S. Tsirkin
parent fd479c60f5
commit 9b02e1618c
2 changed files with 31 additions and 2 deletions
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32
hw/net/virtio-net.c
View File

@ -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),

1
include/hw/virtio/virtio-net.h
View File

@ -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;