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Re: [Qemu-devel] [PATCH v3 1/2] virtio-net: enable configurable tx queue


From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH v3 1/2] virtio-net: enable configurable tx queue size
Date: Mon, 26 Jun 2017 11:18:37 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1



On 2017年06月23日 10:32, Wei Wang wrote:
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 corsses a MemoryRegion thereby
generating more than 1024 iovs after translattion from guest-physical
address in the backend.

Signed-off-by: Wei Wang <address@hidden>
---
  hw/net/virtio-net.c            | 45 +++++++++++++++++++++++++++++++++---------
  include/hw/virtio/virtio-net.h |  1 +
  2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 91eddaf..d13ca60 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -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);
+

Unnecessary whitespace change.

      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 "), "
@@ -1947,17 +1964,11 @@ static void virtio_net_device_realize(DeviceState *dev, 
Error **errp)
          error_report("Defaulting to \"bh\"");
      }
- for (i = 0; i < n->max_queues; i++) {
-        virtio_net_add_queue(n, i);
-    }
-
-    n->ctrl_vq = virtio_add_queue(vdev, 64, virtio_net_handle_ctrl);
      qemu_macaddr_default_if_unset(&n->nic_conf.macaddr);
      memcpy(&n->mac[0], &n->nic_conf.macaddr, sizeof(n->mac));
      n->status = VIRTIO_NET_S_LINK_UP;
      n->announce_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                       virtio_net_announce_timer, n);
-

Unnecessary whitespace change.

      if (n->netclient_type) {
          /*
           * Happen when virtio_net_set_netclient_name has been called.
@@ -1968,6 +1979,21 @@ static void virtio_net_device_realize(DeviceState *dev, 
Error **errp)
          n->nic = qemu_new_nic(&net_virtio_info, &n->nic_conf,
                                object_get_typename(OBJECT(dev)), dev->id, n);
      }
+    nc = qemu_get_queue(n->nic);
+
+    /*
+     * Currently, backends other than vhost-user don't support 1024 queue
+     * size.
+     */
+    if (n->net_conf.tx_queue_size == VIRTQUEUE_MAX_SIZE &&
+        nc->peer->info->type != NET_CLIENT_DRIVER_VHOST_USER) {
+        n->net_conf.tx_queue_size = VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;

Do we really want assume all vhost-user backend support 1024 queue size?

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

Any reason to move virtio_net_add_queue() here?

+    n->ctrl_vq = virtio_add_queue(vdev, 64, virtio_net_handle_ctrl);
peer_test_vnet_hdr(n);
      if (peer_has_vnet_hdr(n)) {
@@ -1990,7 +2016,6 @@ static void virtio_net_device_realize(DeviceState *dev, 
Error **errp)
n->vlans = g_malloc0(MAX_VLAN >> 3); - nc = qemu_get_queue(n->nic);
      nc->rxfilter_notify_enabled = 1;
n->qdev = dev;
@@ -2106,6 +2131,8 @@ 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),
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index 602b486..b81b6a4 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -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;




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