vhost-user: Add 'VHOST_USER_POSTCOPY_ADVISE' message

Wire up a notifier to send a VHOST_USER_POSTCOPY_ADVISE
message on an incoming advise.

Later patches will fill in the behaviour/contents of the
message.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index aab35c4845..ceb17b0554 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -78,6 +78,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_CONFIG = 25,
     VHOST_USER_CREATE_CRYPTO_SESSION = 26,
     VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
+    VHOST_USER_POSTCOPY_ADVISE  = 28,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -795,6 +796,50 @@ out:
     return ret;
 }
 
+/*
+ * Called at the start of an inbound postcopy on reception of the
+ * 'advise' command.
+ */
+static int vhost_user_postcopy_advise(struct vhost_dev *dev, Error **errp)
+{
+    struct vhost_user *u = dev->opaque;
+    CharBackend *chr = u->chr;
+    int ufd;
+    VhostUserMsg msg = {
+        .hdr.request = VHOST_USER_POSTCOPY_ADVISE,
+        .hdr.flags = VHOST_USER_VERSION,
+    };
+
+    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
+        error_setg(errp, "Failed to send postcopy_advise to vhost");
+        return -1;
+    }
+
+    if (vhost_user_read(dev, &msg) < 0) {
+        error_setg(errp, "Failed to get postcopy_advise reply from vhost");
+        return -1;
+    }
+
+    if (msg.hdr.request != VHOST_USER_POSTCOPY_ADVISE) {
+        error_setg(errp, "Unexpected msg type. Expected %d received %d",
+                     VHOST_USER_POSTCOPY_ADVISE, msg.hdr.request);
+        return -1;
+    }
+
+    if (msg.hdr.size) {
+        error_setg(errp, "Received bad msg size.");
+        return -1;
+    }
+    ufd = qemu_chr_fe_get_msgfd(chr);
+    if (ufd < 0) {
+        error_setg(errp, "%s: Failed to get ufd", __func__);
+        return -1;
+    }
+
+    /* TODO: register ufd with userfault thread */
+    return 0;
+}
+
 static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
                                         void *opaque)
 {
@@ -814,6 +859,9 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
         }
         break;
 
+    case POSTCOPY_NOTIFY_INBOUND_ADVISE:
+        return vhost_user_postcopy_advise(dev, pnd->errp);
+
     default:
         /* We ignore notifications we don't know */
         break;