[Qemu-devel] [RFC v3 1/3] vhost-user: Add MTU protocol feature and op

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch implements VHOST_USER_PROTOCOL_F_MTU protocol
feature and VHOST_USER_SET_MTU request so that the backend
gets notified of the user defined host MTU.

Vhost-net driver sends this request through a new
vhost_net_set_mtu vhost_ops entry.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Aaron Conole <aconole@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 docs/specs/vhost-user.txt         | 13 +++++++++++++
 hw/virtio/vhost-user.c            | 13 +++++++++++++
 include/hw/virtio/vhost-backend.h |  2 ++
 3 files changed, 28 insertions(+)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 7890d71..1740baa 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -259,6 +259,7 @@ Protocol features
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD      1
 #define VHOST_USER_PROTOCOL_F_RARP           2
 #define VHOST_USER_PROTOCOL_F_REPLY_ACK      3
+#define VHOST_USER_PROTOCOL_F_MTU            4
 
 Message types
 -------------
@@ -470,6 +471,18 @@ Message types
       The first 6 bytes of the payload contain the mac address of the guest to
       allow the vhost user backend to construct and broadcast the fake RARP.
 
+ * VHOST_USER_SET_MTU
+
+      Id: 20
+	  Equivalent ioctl: N/A
+	  Master payload: u64
+
+	  Set host MTU value exposed to the guest.
+	  This request should be sent only when VIRTIO_NET_F_MTU feature has been
+	  successfully negotiated, VHOST_USER_F_PROTOCOL_FEATURES is present in
+	  VHOST_USER_GET_FEATURES and protocol feature bit VHOST_USER_PROTOCOL_F_MTU
+	  is present in VHOST_USER_GET_PROTOCOL_FEATURES.
+
 VHOST_USER_PROTOCOL_F_REPLY_ACK:
 -------------------------------
 The original vhost-user specification only demands replies for certain
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 7ee92b3..86e8255 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -32,6 +32,7 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
     VHOST_USER_PROTOCOL_F_RARP = 2,
     VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
+    VHOST_USER_PROTOCOL_F_MTU = 4,
 
     VHOST_USER_PROTOCOL_F_MAX
 };
@@ -59,6 +60,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_GET_QUEUE_NUM = 17,
     VHOST_USER_SET_VRING_ENABLE = 18,
     VHOST_USER_SEND_RARP = 19,
+    VHOST_USER_SET_MTU = 20,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -186,6 +188,7 @@ static bool vhost_user_one_time_request(VhostUserRequest request)
     case VHOST_USER_RESET_OWNER:
     case VHOST_USER_SET_MEM_TABLE:
     case VHOST_USER_GET_QUEUE_NUM:
+    case VHOST_USER_SET_MTU:
         return true;
     default:
         return false;
@@ -685,6 +688,15 @@ static bool vhost_user_can_merge(struct vhost_dev *dev,
     return mfd == rfd;
 }
 
+static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
+{
+    if (dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_MTU)) {
+        return vhost_user_set_u64(dev, VHOST_USER_SET_MTU, (uint64_t)mtu);
+    }
+
+    return -1;
+}
+
 const VhostOps user_ops = {
         .backend_type = VHOST_BACKEND_TYPE_USER,
         .vhost_backend_init = vhost_user_init,
@@ -708,4 +720,5 @@ const VhostOps user_ops = {
         .vhost_requires_shm_log = vhost_user_requires_shm_log,
         .vhost_migration_done = vhost_user_migration_done,
         .vhost_backend_can_merge = vhost_user_can_merge,
+        .vhost_net_set_mtu = vhost_user_net_set_mtu,
 };
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index 6e90703..30abc11 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -32,6 +32,7 @@ typedef int (*vhost_backend_memslots_limit)(struct vhost_dev *dev);
 
 typedef int (*vhost_net_set_backend_op)(struct vhost_dev *dev,
                                 struct vhost_vring_file *file);
+typedef int (*vhost_net_set_mtu_op)(struct vhost_dev *dev, uint16_t mtu);
 typedef int (*vhost_scsi_set_endpoint_op)(struct vhost_dev *dev,
                                   struct vhost_scsi_target *target);
 typedef int (*vhost_scsi_clear_endpoint_op)(struct vhost_dev *dev,
@@ -83,6 +84,7 @@ typedef struct VhostOps {
     vhost_backend_cleanup vhost_backend_cleanup;
     vhost_backend_memslots_limit vhost_backend_memslots_limit;
     vhost_net_set_backend_op vhost_net_set_backend;
+    vhost_net_set_mtu_op vhost_net_set_mtu;
     vhost_scsi_set_endpoint_op vhost_scsi_set_endpoint;
     vhost_scsi_clear_endpoint_op vhost_scsi_clear_endpoint;
     vhost_scsi_get_abi_version_op vhost_scsi_get_abi_version;
-- 
2.9.3