[PATCH] vhost-user: add support for VHOST_USER_SET_STATUS

[Maxime Coquelin]

It is usefull for the Vhost-user backend to know
about about the Virtio device status updates,
especially when the driver sets the DRIVER_OK bit.

With that information, no more need to do hazardous
assumptions on when the driver is done with the
device configuration.

Signed-off-by: Maxime Coquelin <address@hidden>
---

This patch applies on top of Cindy's "vDPA support in qemu"
series, which introduces the .vhost_set_state vhost-backend
ops.

 docs/interop/vhost-user.rst | 12 ++++++++++++
 hw/net/vhost_net.c          | 10 +++++-----
 hw/virtio/vhost-user.c      | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
index 3b1b6602c7..f108de7458 100644
--- a/docs/interop/vhost-user.rst
+++ b/docs/interop/vhost-user.rst
@@ -815,6 +815,7 @@ Protocol features
   #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD       12
   #define VHOST_USER_PROTOCOL_F_RESET_DEVICE         13
   #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14
+  #define VHOST_USER_PROTOCOL_F_STATUS               15
 
 Master message types
 --------------------
@@ -1263,6 +1264,17 @@ Master message types
 
   The state.num field is currently reserved and must be set to 0.
 
+``VHOST_USER_SET_STATUS``
+  :id: 36
+  :equivalent ioctl: VHOST_VDPA_SET_STATUS
+  :slave payload: N/A
+  :master payload: ``u64``
+
+  When the ``VHOST_USER_PROTOCOL_F_STATUS`` protocol feature has been
+  successfully negotiated, this message is submitted by the master to
+  notify the backend with updated device status as defined in the Virtio
+  specification.
+
 Slave message types
 -------------------
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 463e333531..37f3156dbc 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -517,10 +517,10 @@ int vhost_set_state(NetClientState *nc, int state)
 {
     struct vhost_net *net = get_vhost_net(nc);
     struct vhost_dev *hdev = &net->dev;
-    if (nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
-        if (hdev->vhost_ops->vhost_set_state) {
-                return hdev->vhost_ops->vhost_set_state(hdev, state);
-             }
-        }
+
+    if (hdev->vhost_ops->vhost_set_state) {
+        return hdev->vhost_ops->vhost_set_state(hdev, state);
+    }
+
     return 0;
 }
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index ec21e8fbe8..b7e52d97fc 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -59,6 +59,7 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
     VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
     VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
+    VHOST_USER_PROTOCOL_F_STATUS = 15,
     VHOST_USER_PROTOCOL_F_MAX
 };
 
@@ -100,6 +101,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_INFLIGHT_FD = 32,
     VHOST_USER_GPU_SET_SOCKET = 33,
     VHOST_USER_RESET_DEVICE = 34,
+    VHOST_USER_SET_STATUS = 36,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -1886,6 +1888,38 @@ static int vhost_user_set_inflight_fd(struct vhost_dev 
*dev,
     return 0;
 }
 
+static int vhost_user_set_state(struct vhost_dev *dev, int state)
+{
+    bool reply_supported = virtio_has_feature(dev->protocol_features,
+                                              VHOST_USER_PROTOCOL_F_REPLY_ACK);
+
+    VhostUserMsg msg = {
+        .hdr.request = VHOST_USER_SET_STATUS,
+        .hdr.flags = VHOST_USER_VERSION,
+        .hdr.size = sizeof(msg.payload.u64),
+        .payload.u64 = (uint64_t)state,
+    };
+
+    if (!virtio_has_feature(dev->protocol_features,
+                VHOST_USER_PROTOCOL_F_STATUS)) {
+        return -1;
+    }
+
+    if (reply_supported) {
+        msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
+    }
+
+    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
+        return -1;
+    }
+
+    if (reply_supported) {
+        return process_message_reply(dev, &msg);
+    }
+
+    return 0;
+}
+
 bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp)
 {
     if (user->chr) {
@@ -1947,4 +1981,5 @@ const VhostOps user_ops = {
         .vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
         .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
         .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
+        .vhost_set_state = vhost_user_set_state,
 };
-- 
2.25.4