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Re: [Qemu-devel] [PATCH v11 6/7] vhost-user: add multiple queue support


From: Yuanhan Liu
Subject: Re: [Qemu-devel] [PATCH v11 6/7] vhost-user: add multiple queue support
Date: Wed, 23 Sep 2015 14:56:42 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, Sep 23, 2015 at 12:20:00PM +0800, Yuanhan Liu wrote:
> From: Changchun Ouyang <address@hidden>
> 
[...]
>  static void net_vhost_user_event(void *opaque, int event)
>  {
> -    VhostUserState *s = opaque;
> +    const char *name = opaque;
> +    NetClientState *ncs[MAX_QUEUE_NUM];
> +    VhostUserState *s;
> +    Error *err = NULL;
> +    int queues;
>  
> +    queues = qemu_find_net_clients_except(name, ncs,
> +                                          NET_CLIENT_OPTIONS_KIND_NIC,
> +                                          MAX_QUEUE_NUM);
> +    s = DO_UPCAST(VhostUserState, nc, ncs[0]);
>      switch (event) {
>      case CHR_EVENT_OPENED:
> -        vhost_user_start(s);
> -        net_vhost_link_down(s, false);
> +        if (vhost_user_start(queues, ncs) < 0) {
> +            exit(1);
> +        }
> +        qmp_set_link(name, true, &err);
>          error_report("chardev \"%s\" went up", s->chr->label);
>          break;
>      case CHR_EVENT_CLOSED:
> -        net_vhost_link_down(s, true);
> -        vhost_user_stop(s);
> +        qmp_set_link(name, true, &err);
> +        vhost_user_stop(queues, ncs);

Sigh... A silly Copy & Paste typo. Here is the udpated patch:

        --yliu

---8<---
>From 3793772867024dfabb9eb8eb5c53ae6714f88618 Mon Sep 17 00:00:00 2001
From: Changchun Ouyang <address@hidden>
Date: Tue, 15 Sep 2015 14:28:38 +0800
Subject: [PATCH v11 6/7] vhost-user: add multiple queue support

This patch is initially based a patch from Nikolay Nikolaev.

This patch adds vhost-user multiple queue support, by creating a nc
and vhost_net pair for each queue.

Qemu exits if find that the backend can't support the number of requested
queues (by providing queues=# option). The max number is queried by a
new message, VHOST_USER_GET_QUEUE_NUM, and is sent only when protocol
feature VHOST_USER_PROTOCOL_F_MQ is present first.

The max queue check is done at vhost-user initiation stage. We initiate
one queue first, which, in the meantime, also gets the max_queues the
backend supports.

In older version, it was reported that some messages are sent more times
than necessary. Here we came an agreement with Michael that we could
categorize vhost user messages to 2 types: non-vring specific messages,
which should be sent only once, and vring specific messages, which should
be sent per queue.

Here I introduced a helper function vhost_user_one_time_request(), which
lists following messages as non-vring specific messages:

        VHOST_USER_SET_OWNER
        VHOST_USER_RESET_DEVICE
        VHOST_USER_SET_MEM_TABLE
        VHOST_USER_GET_QUEUE_NUM

For above messages, we simply ignore them when they are not sent the first
time.

Signed-off-by: Nikolay Nikolaev <address@hidden>
Signed-off-by: Changchun Ouyang <address@hidden>
Signed-off-by: Yuanhan Liu <address@hidden>

---
v11: inovke qmp_set_link() directly -- Suggested by Jason Wang

v10: don't treat VHOST_USER_SET/GET_[PROTOCOL]_FEATURES as one time
     request, as the two feature bits need to be stored at per-device.

v9: per suggested by Jason Wang, we could invoke qemu_chr_add_handlers()
    once only, and invoke qemu_find_net_clients_except() at the handler
    to gather all related ncs, for initiating all queues. Which addresses
    a hidden bug in older verion in a more QEMU-like way.

v8: set net->dev.vq_index correctly inside vhost_net_init() based on the
    value from net->nc->queue_index.
---
 docs/specs/vhost-user.txt |  15 +++++
 hw/net/vhost_net.c        |  10 ++--
 hw/virtio/vhost-user.c    |  22 ++++++++
 hw/virtio/vhost.c         |   5 +-
 net/vhost-user.c          | 141 ++++++++++++++++++++++++++++++----------------
 qapi-schema.json          |   6 +-
 qemu-options.hx           |   5 +-
 7 files changed, 147 insertions(+), 57 deletions(-)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 43db9b4..cfc9d41 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -135,6 +135,21 @@ As older slaves don't support negotiating protocol 
features,
 a feature bit was dedicated for this purpose:
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
+Multiple queue support
+----------------------
+
+Multiple queue is treated as a protocol extension, hence the slave has to
+implement protocol features first. The multiple queues feature is supported
+only when the protocol feature VHOST_USER_PROTOCOL_F_MQ (bit 0) is set:
+#define VHOST_USER_PROTOCOL_F_MQ    0
+
+The max number of queues the slave supports can be queried with message
+VHOST_USER_GET_PROTOCOL_FEATURES. Master should stop when the number of
+requested queues is bigger than that.
+
+As all queues share one connection, the master uses a unique index for each
+queue in the sent message to identify a specified queue.
+
 Message types
 -------------
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index f663e5a..ad82b5c 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -148,8 +148,11 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
         fprintf(stderr, "vhost-net requires net backend to be setup\n");
         goto fail;
     }
+    net->nc = options->net_backend;
 
     net->dev.max_queues = 1;
+    net->dev.nvqs = 2;
+    net->dev.vqs = net->vqs;
 
     if (backend_kernel) {
         r = vhost_net_get_fd(options->net_backend);
@@ -164,11 +167,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
         net->dev.backend_features = 0;
         net->dev.protocol_features = 0;
         net->backend = -1;
-    }
-    net->nc = options->net_backend;
 
-    net->dev.nvqs = 2;
-    net->dev.vqs = net->vqs;
+        /* vhost-user needs vq_index to initiate a specific queue pair */
+        net->dev.vq_index = net->nc->queue_index * net->dev.nvqs;
+    }
 
     r = vhost_dev_init(&net->dev, options->opaque,
                        options->backend_type);
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 5018fd6..e42fde6 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -187,6 +187,19 @@ static int vhost_user_write(struct vhost_dev *dev, 
VhostUserMsg *msg,
             0 : -1;
 }
 
+static bool vhost_user_one_time_request(VhostUserRequest request)
+{
+    switch (request) {
+    case VHOST_USER_SET_OWNER:
+    case VHOST_USER_RESET_DEVICE:
+    case VHOST_USER_SET_MEM_TABLE:
+    case VHOST_USER_GET_QUEUE_NUM:
+        return true;
+    default:
+        return false;
+    }
+}
+
 static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
         void *arg)
 {
@@ -207,6 +220,15 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned 
long int request,
         msg_request = request;
     }
 
+    /*
+     * For non-vring specific requests, like VHOST_USER_SET_MEM_TABLE,
+     * we just need send it once in the first time. For later such
+     * request, we just ignore it.
+     */
+    if (vhost_user_one_time_request(msg_request) && dev->vq_index != 0) {
+        return 0;
+    }
+
     msg.request = msg_request;
     msg.flags = VHOST_USER_VERSION;
     msg.size = 0;
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 7a7812d..c0ed5b2 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -874,8 +874,9 @@ static void vhost_eventfd_del(MemoryListener *listener,
 static int vhost_virtqueue_init(struct vhost_dev *dev,
                                 struct vhost_virtqueue *vq, int n)
 {
+    int vhost_vq_index = dev->vhost_ops->vhost_backend_get_vq_index(dev, n);
     struct vhost_vring_file file = {
-        .index = n,
+        .index = vhost_vq_index,
     };
     int r = event_notifier_init(&vq->masked_notifier, 0);
     if (r < 0) {
@@ -926,7 +927,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     }
 
     for (i = 0; i < hdev->nvqs; ++i) {
-        r = vhost_virtqueue_init(hdev, hdev->vqs + i, i);
+        r = vhost_virtqueue_init(hdev, hdev->vqs + i, hdev->vq_index + i);
         if (r < 0) {
             goto fail_vq;
         }
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 93dcecd..1abec97 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -14,6 +14,7 @@
 #include "sysemu/char.h"
 #include "qemu/config-file.h"
 #include "qemu/error-report.h"
+#include "qmp-commands.h"
 
 typedef struct VhostUserState {
     NetClientState nc;
@@ -39,37 +40,77 @@ static int vhost_user_running(VhostUserState *s)
     return (s->vhost_net) ? 1 : 0;
 }
 
-static int vhost_user_start(VhostUserState *s)
+static void vhost_user_stop(int queues, NetClientState *ncs[])
 {
-    VhostNetOptions options;
-
-    if (vhost_user_running(s)) {
-        return 0;
-    }
+    VhostUserState *s;
+    int i;
 
-    options.backend_type = VHOST_BACKEND_TYPE_USER;
-    options.net_backend = &s->nc;
-    options.opaque = s->chr;
+    for (i = 0; i < queues; i++) {
+        assert (ncs[i]->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
 
-    s->vhost_net = vhost_net_init(&options);
+        s = DO_UPCAST(VhostUserState, nc, ncs[i]);
+        if (!vhost_user_running(s)) {
+            continue;
+        }
 
-    return vhost_user_running(s) ? 0 : -1;
+        if (s->vhost_net) {
+            vhost_net_cleanup(s->vhost_net);
+            s->vhost_net = NULL;
+        }
+    }
 }
 
-static void vhost_user_stop(VhostUserState *s)
+static int vhost_user_start(int queues, NetClientState *ncs[])
 {
-    if (vhost_user_running(s)) {
-        vhost_net_cleanup(s->vhost_net);
+    VhostNetOptions options;
+    VhostUserState *s;
+    int max_queues;
+    int i;
+
+    options.backend_type = VHOST_BACKEND_TYPE_USER;
+
+    for (i = 0; i < queues; i++) {
+        assert (ncs[i]->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
+
+        s = DO_UPCAST(VhostUserState, nc, ncs[i]);
+        if (vhost_user_running(s)) {
+            continue;
+        }
+
+        options.net_backend = ncs[i];
+        options.opaque      = s->chr;
+        s->vhost_net = vhost_net_init(&options);
+        if (!s->vhost_net) {
+            error_report("failed to init vhost_net for queue %d\n", i);
+            goto err;
+        }
+
+        if (i == 0) {
+            max_queues = vhost_net_get_max_queues(s->vhost_net);
+            if (queues > max_queues) {
+                error_report("you are asking more queues than "
+                             "supported: %d\n", max_queues);
+                goto err;
+            }
+        }
     }
 
-    s->vhost_net = 0;
+    return 0;
+
+err:
+    vhost_user_stop(i + 1, ncs);
+    return -1;
 }
 
 static void vhost_user_cleanup(NetClientState *nc)
 {
     VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
 
-    vhost_user_stop(s);
+    if (s->vhost_net) {
+        vhost_net_cleanup(s->vhost_net);
+        s->vhost_net = NULL;
+    }
+
     qemu_purge_queued_packets(nc);
 }
 
@@ -95,59 +136,61 @@ static NetClientInfo net_vhost_user_info = {
         .has_ufo = vhost_user_has_ufo,
 };
 
-static void net_vhost_link_down(VhostUserState *s, bool link_down)
-{
-    s->nc.link_down = link_down;
-
-    if (s->nc.peer) {
-        s->nc.peer->link_down = link_down;
-    }
-
-    if (s->nc.info->link_status_changed) {
-        s->nc.info->link_status_changed(&s->nc);
-    }
-
-    if (s->nc.peer && s->nc.peer->info->link_status_changed) {
-        s->nc.peer->info->link_status_changed(s->nc.peer);
-    }
-}
-
 static void net_vhost_user_event(void *opaque, int event)
 {
-    VhostUserState *s = opaque;
+    const char *name = opaque;
+    NetClientState *ncs[MAX_QUEUE_NUM];
+    VhostUserState *s;
+    Error *err = NULL;
+    int queues;
 
+    queues = qemu_find_net_clients_except(name, ncs,
+                                          NET_CLIENT_OPTIONS_KIND_NIC,
+                                          MAX_QUEUE_NUM);
+    s = DO_UPCAST(VhostUserState, nc, ncs[0]);
     switch (event) {
     case CHR_EVENT_OPENED:
-        vhost_user_start(s);
-        net_vhost_link_down(s, false);
+        if (vhost_user_start(queues, ncs) < 0) {
+            exit(1);
+        }
+        qmp_set_link(name, true, &err);
         error_report("chardev \"%s\" went up", s->chr->label);
         break;
     case CHR_EVENT_CLOSED:
-        net_vhost_link_down(s, true);
-        vhost_user_stop(s);
+        qmp_set_link(name, false, &err);
+        vhost_user_stop(queues, ncs);
         error_report("chardev \"%s\" went down", s->chr->label);
         break;
     }
+
+    if (err) {
+        error_report_err(err);
+    }
 }
 
 static int net_vhost_user_init(NetClientState *peer, const char *device,
-                               const char *name, CharDriverState *chr)
+                               const char *name, CharDriverState *chr,
+                               int 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);
+        /* We don't provide a receive callback */
+        nc->receive_disabled = 1;
+        nc->queue_index = i;
 
-    /* We don't provide a receive callback */
-    s->nc.receive_disabled = 1;
-    s->chr = chr;
+        s = DO_UPCAST(VhostUserState, nc, nc);
+        s->chr = chr;
+    }
 
-    qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
+    qemu_chr_add_handlers(chr, NULL, NULL, net_vhost_user_event, (void*)name);
 
     return 0;
 }
@@ -226,6 +269,7 @@ static int net_vhost_check_net(void *opaque, QemuOpts 
*opts, Error **errp)
 int net_init_vhost_user(const NetClientOptions *opts, const char *name,
                         NetClientState *peer, Error **errp)
 {
+    int queues;
     const NetdevVhostUserOptions *vhost_user_opts;
     CharDriverState *chr;
 
@@ -243,6 +287,7 @@ int net_init_vhost_user(const NetClientOptions *opts, const 
char *name,
         return -1;
     }
 
+    queues = vhost_user_opts->has_queues ? vhost_user_opts->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 527690d..582a817 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2481,12 +2481,16 @@
 #
 # @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':        'int' } }
 
 ##
 # @NetClientOptions
diff --git a/qemu-options.hx b/qemu-options.hx
index 7e147b8..328404c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1990,13 +1990,14 @@ 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
-- 
1.9.0




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