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Re: [Qemu-devel] [PATCH v5] vhost-user: add multi queue support


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH v5] vhost-user: add multi queue support
Date: Sun, 30 Aug 2015 18:28:00 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

On 05/28/2015 04:23 AM, Ouyang Changchun wrote:
Based on patch by Nikolay Nikolaev:
Vhost-user will implement the multi queue support in a similar way
to what vhost already has - a separate thread for each queue.
To enable the multi queue functionality - a new command line parameter
"queues" is introduced for the vhost-user netdev.

Signed-off-by: Nikolay Nikolaev <address@hidden>
Signed-off-by: Changchun Ouyang <address@hidden>
Hi,

Can you please share how you did you test it?
Was it the DPDK vhost-user example? (after the MQ patches, of course)
I ask because I tried to test it with no success so far.
Any pointers would be appreciated.

Thanks,
Marcel


---
Changes since v4:
  - remove the unnecessary trailing '\n'

Changes since v3:
  - fix one typo and wrap one long line

Changes since v2:
  - fix vq index issue for set_vring_call
    When it is the case of VHOST_SET_VRING_CALL, The vq_index is not 
initialized before it is used,
    thus it could be a random value. The random value leads to crash in vhost 
after passing down
    to vhost, as vhost use this random value to index an array index.
  - fix the typo in the doc and description
  - address vq index for reset_owner

Changes since v1:
  - use s->nc.info_str when bringing up/down the backend

  docs/specs/vhost-user.txt |  5 +++++
  hw/net/vhost_net.c        |  3 ++-
  hw/virtio/vhost-user.c    | 11 ++++++++++-
  net/vhost-user.c          | 37 ++++++++++++++++++++++++-------------
  qapi-schema.json          |  6 +++++-
  qemu-options.hx           |  5 +++--
  6 files changed, 49 insertions(+), 18 deletions(-)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 650bb18..2c8e934 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -127,6 +127,11 @@ in the ancillary data:
  If Master is unable to send the full message or receives a wrong reply it will
  close the connection. An optional reconnection mechanism can be implemented.

+Multi queue support
+-------------------
+The protocol supports multiple queues by setting all index fields in the sent
+messages to a properly calculated value.
+
  Message types
  -------------

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 47f8b89..426b23e 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -157,6 +157,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)

      net->dev.nvqs = 2;
      net->dev.vqs = net->vqs;
+    net->dev.vq_index = net->nc->queue_index;

      r = vhost_dev_init(&net->dev, options->opaque,
                         options->backend_type, options->force);
@@ -267,7 +268,7 @@ static void vhost_net_stop_one(struct vhost_net *net,
          for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
              const VhostOps *vhost_ops = net->dev.vhost_ops;
              int r = vhost_ops->vhost_call(&net->dev, VHOST_RESET_OWNER,
-                                          NULL);
+                                          &file);
              assert(r >= 0);
          }
      }
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index e7ab829..d6f2163 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -210,7 +210,12 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned 
long int request,
          break;

      case VHOST_SET_OWNER:
+        break;
+
      case VHOST_RESET_OWNER:
+        memcpy(&msg.state, arg, sizeof(struct vhost_vring_state));
+        msg.state.index += dev->vq_index;
+        msg.size = sizeof(m.state);
          break;

      case VHOST_SET_MEM_TABLE:
@@ -253,17 +258,20 @@ static int vhost_user_call(struct vhost_dev *dev, 
unsigned long int request,
      case VHOST_SET_VRING_NUM:
      case VHOST_SET_VRING_BASE:
          memcpy(&msg.state, arg, sizeof(struct vhost_vring_state));
+        msg.state.index += dev->vq_index;
          msg.size = sizeof(m.state);
          break;

      case VHOST_GET_VRING_BASE:
          memcpy(&msg.state, arg, sizeof(struct vhost_vring_state));
+        msg.state.index += dev->vq_index;
          msg.size = sizeof(m.state);
          need_reply = 1;
          break;

      case VHOST_SET_VRING_ADDR:
          memcpy(&msg.addr, arg, sizeof(struct vhost_vring_addr));
+        msg.addr.index += dev->vq_index;
          msg.size = sizeof(m.addr);
          break;

@@ -271,7 +279,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned 
long int request,
      case VHOST_SET_VRING_CALL:
      case VHOST_SET_VRING_ERR:
          file = arg;
-        msg.u64 = file->index & VHOST_USER_VRING_IDX_MASK;
+        msg.u64 = (file->index + dev->vq_index) & VHOST_USER_VRING_IDX_MASK;
          msg.size = sizeof(m.u64);
          if (ioeventfd_enabled() && file->fd > 0) {
              fds[fd_num++] = file->fd;
@@ -313,6 +321,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned 
long int request,
                  error_report("Received bad msg size.");
                  return -1;
              }
+            msg.state.index -= dev->vq_index;
              memcpy(arg, &msg.state, sizeof(struct vhost_vring_state));
              break;
          default:
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 1d86a2b..904d8af 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -121,35 +121,39 @@ static void net_vhost_user_event(void *opaque, int event)
      case CHR_EVENT_OPENED:
          vhost_user_start(s);
          net_vhost_link_down(s, false);
-        error_report("chardev \"%s\" went up", s->chr->label);
+        error_report("chardev \"%s\" went up", s->nc.info_str);
          break;
      case CHR_EVENT_CLOSED:
          net_vhost_link_down(s, true);
          vhost_user_stop(s);
-        error_report("chardev \"%s\" went down", s->chr->label);
+        error_report("chardev \"%s\" went down", s->nc.info_str);
          break;
      }
  }

  static int net_vhost_user_init(NetClientState *peer, const char *device,
-                               const char *name, CharDriverState *chr)
+                               const char *name, CharDriverState *chr,
+                               uint32_t queues)
  {
      NetClientState *nc;
      VhostUserState *s;
+    int i;

-    nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
+    for (i = 0; i < queues; i++) {
+        nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);

-    snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user to %s",
-             chr->label);
+        snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user%d to %s",
+                 i, chr->label);

-    s = DO_UPCAST(VhostUserState, nc, nc);
+        s = DO_UPCAST(VhostUserState, nc, nc);

-    /* We don't provide a receive callback */
-    s->nc.receive_disabled = 1;
-    s->chr = chr;
-
-    qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
+        /* We don't provide a receive callback */
+        s->nc.receive_disabled = 1;
+        s->chr = chr;
+        s->nc.queue_index = i;

+        qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
+    }
      return 0;
  }

@@ -225,6 +229,7 @@ static int net_vhost_check_net(QemuOpts *opts, void *opaque)
  int net_init_vhost_user(const NetClientOptions *opts, const char *name,
                          NetClientState *peer)
  {
+    uint32_t queues;
      const NetdevVhostUserOptions *vhost_user_opts;
      CharDriverState *chr;

@@ -243,6 +248,12 @@ int net_init_vhost_user(const NetClientOptions *opts, 
const char *name,
          return -1;
      }

+    /* number of queues for multiqueue */
+    if (vhost_user_opts->has_queues) {
+        queues = vhost_user_opts->queues;
+    } else {
+        queues = 1;
+    }

-    return net_vhost_user_init(peer, "vhost_user", name, chr);
+    return net_vhost_user_init(peer, "vhost_user", name, chr, queues);
  }
diff --git a/qapi-schema.json b/qapi-schema.json
index f97ffa1..00791dd 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2444,12 +2444,16 @@
  #
  # @vhostforce: #optional vhost on for non-MSIX virtio guests (default: false).
  #
+# @queues: #optional number of queues to be created for multiqueue vhost-user
+#          (default: 1) (Since 2.4)
+#
  # Since 2.1
  ##
  { 'struct': 'NetdevVhostUserOptions',
    'data': {
      'chardev':        'str',
-    '*vhostforce':    'bool' } }
+    '*vhostforce':    'bool',
+    '*queues':        'uint32' } }

  ##
  # @NetClientOptions
diff --git a/qemu-options.hx b/qemu-options.hx
index ec356f6..dad035e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1942,13 +1942,14 @@ The hubport netdev lets you connect a NIC to a QEMU 
"vlan" instead of a single
  netdev.  @code{-net} and @code{-device} with parameter @option{vlan} create 
the
  required hub automatically.

address@hidden -netdev vhost-user,address@hidden,vhostforce=on|off]
address@hidden -netdev vhost-user,address@hidden,vhostforce=on|off][,queues=n]

  Establish a vhost-user netdev, backed by a chardev @var{id}. The chardev 
should
  be a unix domain socket backed one. The vhost-user uses a specifically defined
  protocol to pass vhost ioctl replacement messages to an application on the 
other
  end of the socket. On non-MSIX guests, the feature can be forced with
address@hidden
address@hidden Use 'address@hidden' to specify the number of queues to
+be created for multiqueue vhost-user.

  Example:
  @example





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