[Qemu-devel] [PATCH v6 1/2] vhost-user: add multi queue support

[Ouyang Changchun <changchun.ouyang@intel.com>]

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.

The RESET_OWNER change is based on commit:
   294ce717e0f212ed0763307f3eab72b4a1bdf4d0
If it is reverted, the patch need update for it accordingly.

Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
---
Changes since v5:
 - fix the message descption for VHOST_RESET_OWNER in vhost-user txt

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 |  7 ++++++-
 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, 50 insertions(+), 19 deletions(-)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 70da3b1..9390f89 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -135,6 +135,11 @@ As older slaves don't support negotiating protocol features,
 a feature bit was dedicated for this purpose:
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
+Multi queue support
+-------------------
+The protocol supports multiple queues by setting all index fields in the sent
+messages to a properly calculated value.
+
 Message types
 -------------
 
@@ -198,7 +203,7 @@ Message types
 
       Id: 4
       Equivalent ioctl: VHOST_RESET_OWNER
-      Master payload: N/A
+      Master payload: vring state description
 
       Issued when a new connection is about to be closed. The Master will no
       longer own this connection (and will usually close it).
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 1f25cb3..9cd6c05 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -159,6 +159,7 @@ 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);
@@ -269,7 +270,7 @@ 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 27ba035..fb11d4c 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -219,7 +219,12 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
         break;
 
     case VHOST_USER_SET_OWNER:
+        break;
+
     case VHOST_USER_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_USER_SET_MEM_TABLE:
@@ -262,17 +267,20 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
     case VHOST_USER_SET_VRING_NUM:
     case VHOST_USER_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_USER_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_USER_SET_VRING_ADDR:
         memcpy(&msg.addr, arg, sizeof(struct vhost_vring_addr));
+        msg.addr.index += dev->vq_index;
         msg.size = sizeof(m.addr);
         break;
 
@@ -280,7 +288,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
     case VHOST_USER_SET_VRING_CALL:
     case VHOST_USER_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;
@@ -322,6 +330,7 @@ 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..51e40ce 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 2.5)
+#
 # 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.
 
-@item -netdev vhost-user,chardev=@var{id}[,vhostforce=on|off]
+@item -netdev vhost-user,chardev=@var{id}[,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
-@var{vhostforce}.
+@var{vhostforce}. Use 'queues=@var{n}' to specify the number of queues to
+be created for multiqueue vhost-user.
 
 Example:
 @example
-- 
1.8.4.2