[Qemu-devel] [RFC v2 26/32] vhost: Add VHOST_USER_POSTCOPY_END message

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <address@hidden>

This message is sent just before the end of postcopy to get the
client to stop using userfault since we wont respond to any more
requests.  It should close userfaultfd so that any other pages
get mapped to the backing file automatically by the kernel, since
at this point we know we've received everything.

Signed-off-by: Dr. David Alan Gilbert <address@hidden>
---
 contrib/libvhost-user/libvhost-user.c | 23 +++++++++++++++++++++++
 contrib/libvhost-user/libvhost-user.h |  1 +
 docs/interop/vhost-user.txt           |  8 ++++++++
 hw/virtio/vhost-user.c                |  1 +
 4 files changed, 33 insertions(+)

diff --git a/contrib/libvhost-user/libvhost-user.c 
b/contrib/libvhost-user/libvhost-user.c
index d816851c6d..23bff47649 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -67,6 +67,7 @@ vu_request_to_string(int req)
         REQ(VHOST_USER_SET_VRING_ENDIAN),
         REQ(VHOST_USER_POSTCOPY_ADVISE),
         REQ(VHOST_USER_POSTCOPY_LISTEN),
+        REQ(VHOST_USER_POSTCOPY_END),
         REQ(VHOST_USER_MAX),
     };
 #undef REQ
@@ -893,6 +894,26 @@ vu_set_postcopy_listen(VuDev *dev, VhostUserMsg *vmsg)
     vmsg->payload.u64 = 0; /* Success */
     return true;
 }
+
+static bool
+vu_set_postcopy_end(VuDev *dev, VhostUserMsg *vmsg)
+{
+    DPRINT("%s: Entry\n", __func__);
+    dev->postcopy_listening = false;
+    if (dev->postcopy_ufd > 0) {
+        close(dev->postcopy_ufd);
+        dev->postcopy_ufd = -1;
+        DPRINT("%s: Done close\n", __func__);
+    }
+
+    vmsg->fd_num = 0;
+    vmsg->payload.u64 = 0;
+    vmsg->size = sizeof(vmsg->payload.u64);
+    vmsg->flags = VHOST_USER_VERSION |  VHOST_USER_REPLY_MASK;
+    DPRINT("%s: exit\n", __func__);
+    return true;
+}
+
 static bool
 vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
 {
@@ -962,6 +983,8 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
         return vu_set_postcopy_advise(dev, vmsg);
     case VHOST_USER_POSTCOPY_LISTEN:
         return vu_set_postcopy_listen(dev, vmsg);
+    case VHOST_USER_POSTCOPY_END:
+        return vu_set_postcopy_end(dev, vmsg);
     default:
         vmsg_close_fds(vmsg);
         vu_panic(dev, "Unhandled request: %d", vmsg->request);
diff --git a/contrib/libvhost-user/libvhost-user.h 
b/contrib/libvhost-user/libvhost-user.h
index 29c11ba56c..a78596e6fd 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -68,6 +68,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_ENDIAN = 23,
     VHOST_USER_POSTCOPY_ADVISE  = 24,
     VHOST_USER_POSTCOPY_LISTEN  = 25,
+    VHOST_USER_POSTCOPY_END     = 26,
     VHOST_USER_MAX
 } VhostUserRequest;
 
diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index b2a548c94d..d6586e0b43 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -627,6 +627,14 @@ Master message types
 
       Master advises slave that a transition to postcopy mode has happened.
 
+ * VHOST_USER_POSTCOPY_END
+      Id: 26
+      Slave payload: u64
+
+      Master advises that postcopy migration has now completed.  The
+      slave must disable the userfaultfd. The response is an acknowledgement
+      only.
+
 Slave message types
 -------------------
 
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 4d03383a66..c2e55be0fd 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -71,6 +71,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_ENDIAN = 23,
     VHOST_USER_POSTCOPY_ADVISE  = 24,
     VHOST_USER_POSTCOPY_LISTEN  = 25,
+    VHOST_USER_POSTCOPY_END     = 26,
     VHOST_USER_MAX
 } VhostUserRequest;
 
-- 
2.13.5