[Qemu-devel] [PATCH v6 2/2] vhost-user: new protocol feature for multi queue

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

This patch is based on top of "vhost-user: protocol updates" series
proposed earlier by Michael S. Tsirkin.

Use new message VHOST_USER_SET_VRING_FLAG to enable and disable an
actual virt queue, which is similar to attach/detach queue for tap device.
virtio driver on guest doesn't have to use max virt queue pair, it could
enable any number of virt queue ranging from 1 to max virt queue pair.

It requires that VHOST_USER_F_PROTOCOL_FEATURES is present.

Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
---
This is added since v5

 docs/specs/vhost-user.txt         | 17 +++++++++++++++++
 hw/net/vhost_net.c                | 18 ++++++++++++++++++
 hw/net/virtio-net.c               |  2 ++
 hw/virtio/vhost-user.c            | 35 +++++++++++++++++++++++++++++++++--
 include/hw/virtio/vhost-backend.h |  2 ++
 include/net/vhost_net.h           |  1 +
 6 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 9390f89..cca3e5b 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -135,6 +135,10 @@ As older slaves don't support negotiating protocol features,
 a feature bit was dedicated for this purpose:
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
+The Slave uses vring flag to notify the vhost-user whether one virtq is enabled
+or not. This request doesn't require replies:
+#define VHOST_USER_PROTOCOL_F_VRING_FLAG 2
+
 Multi queue support
 -------------------
 The protocol supports multiple queues by setting all index fields in the sent
@@ -306,3 +310,16 @@ Message types
       Bits (0-7) of the payload contain the vring index. Bit 8 is the
       invalid FD flag. This flag is set when there is no file descriptor
       in the ancillary data.
+
+ * VHOST_USER_SET_VRING_FLAG
+
+      Id: 18
+      Equivalent ioctl: N/A
+      Master payload: vring state description
+
+      Set the flag(enable or disable) in the vring, the vhost user backend
+      enable or disable the vring according to state.num. Olny legal if feature
+      bit VHOST_USER_F_PROTOCOL_FEATURES is present in VHOST_USER_GET_FEATURE
+      and feature bit VHOST_USER_PROTOCOL_F_VRING_FLAG is present in
+      VHOST_USER_GET_PROTOCOL_FEATURES. The vring is enabled when state.num is
+      1, otherwise, the vring is disabled.
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 9cd6c05..5fa341c 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -405,6 +405,19 @@ VHostNetState *get_vhost_net(NetClientState *nc)
 
     return vhost_net;
 }
+
+int vhost_set_vring_flag(NetClientState *nc, unsigned int enable)
+{
+    if (nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
+        struct vhost_net *net = get_vhost_net(nc);
+        const VhostOps *vhost_ops = net->dev.vhost_ops;
+        if (vhost_ops->vhost_backend_mq_set_vring_flag)
+            return vhost_ops->vhost_backend_mq_set_vring_flag(&net->dev, enable);
+    }
+
+    return 0;
+}
+
 #else
 struct vhost_net *vhost_net_init(VhostNetOptions *options)
 {
@@ -455,4 +468,9 @@ VHostNetState *get_vhost_net(NetClientState *nc)
 {
     return 0;
 }
+
+int vhost_set_vring_flag(NetClientState *nc, unsigned int enable)
+{
+    return 0;
+}
 #endif
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3af6faf..272b77d 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -396,6 +396,7 @@ static int peer_attach(VirtIONet *n, int index)
     }
 
     if (nc->peer->info->type != NET_CLIENT_OPTIONS_KIND_TAP) {
+        vhost_set_vring_flag(nc->peer, 1);
         return 0;
     }
 
@@ -411,6 +412,7 @@ static int peer_detach(VirtIONet *n, int index)
     }
 
     if (nc->peer->info->type !=  NET_CLIENT_OPTIONS_KIND_TAP) {
+        vhost_set_vring_flag(nc->peer, 0);
         return 0;
     }
 
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index fb11d4c..d806ce2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -25,7 +25,8 @@
 
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
-#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
+#define VHOST_USER_PROTOCOL_F_VRING_FLAG 2
+#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x7ULL
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,
@@ -45,6 +46,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_ERR = 14,
     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+    VHOST_USER_SET_VRING_FLAG = 18,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -399,6 +401,34 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
     return 0;
 }
 
+static int vhost_user_set_vring_flag(struct vhost_dev *dev, unsigned int enable)
+{
+    VhostUserMsg msg = { 0 };
+    int err;
+
+    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
+
+    if ((dev->backend_features & ( 1ULL << VHOST_USER_F_PROTOCOL_FEATURES)) == 0)
+        return -1;
+
+    if ((dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_VRING_FLAG)) == 0)
+        return -1;
+
+    msg.request = VHOST_USER_SET_VRING_FLAG;
+    msg.flags = VHOST_USER_VERSION;
+    /* Set the virt queue pair index */
+    msg.state.index = dev->vq_index / 2;
+    msg.state.num = enable;
+    msg.size = sizeof msg.state;
+
+    err = vhost_user_write(dev, &msg, NULL, 0);
+    if (err < 0) {
+        return err;
+    }
+
+    return 0;
+}
+
 static int vhost_user_cleanup(struct vhost_dev *dev)
 {
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
@@ -412,5 +442,6 @@ const VhostOps user_ops = {
         .backend_type = VHOST_BACKEND_TYPE_USER,
         .vhost_call = vhost_user_call,
         .vhost_backend_init = vhost_user_init,
-        .vhost_backend_cleanup = vhost_user_cleanup
+        .vhost_backend_cleanup = vhost_user_cleanup,
+        .vhost_backend_mq_set_vring_flag = vhost_user_set_vring_flag,
         };
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index e472f29..c394147 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -24,12 +24,14 @@ typedef int (*vhost_call)(struct vhost_dev *dev, unsigned long int request,
              void *arg);
 typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
 typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
+typedef int (*vhost_backend_mq_set_vring_flag)(struct vhost_dev *dev, unsigned int enable);
 
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_call vhost_call;
     vhost_backend_init vhost_backend_init;
     vhost_backend_cleanup vhost_backend_cleanup;
+    vhost_backend_mq_set_vring_flag vhost_backend_mq_set_vring_flag;
 } VhostOps;
 
 extern const VhostOps user_ops;
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index b1c18a3..9b76548 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -29,4 +29,5 @@ bool vhost_net_virtqueue_pending(VHostNetState *net, int n);
 void vhost_net_virtqueue_mask(VHostNetState *net, VirtIODevice *dev,
                               int idx, bool mask);
 VHostNetState *get_vhost_net(NetClientState *nc);
+int vhost_set_vring_flag(NetClientState * nc, unsigned int enable);
 #endif
-- 
1.8.4.2