[Qemu-devel] [RFC v2 14/32] vhost+postcopy: Transmit 'listen' to client

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Notify the vhost-user client on reception of the 'postcopy-listen'
event from the source.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 contrib/libvhost-user/libvhost-user.c | 21 +++++++++++++++++++++
 contrib/libvhost-user/libvhost-user.h |  2 ++
 docs/interop/vhost-user.txt           |  6 ++++++
 hw/virtio/trace-events                |  3 +++
 hw/virtio/vhost-user.c                | 30 ++++++++++++++++++++++++++++++
 migration/postcopy-ram.h              |  1 +
 migration/savevm.c                    |  7 +++++++
 7 files changed, 70 insertions(+)

diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index f9b5b12b28..e8accf11db 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -15,7 +15,9 @@
 
 #include <qemu/osdep.h>
 #include <sys/eventfd.h>
+#include <sys/ioctl.h>
 #include <sys/syscall.h>
+#include <linux/userfaultfd.h>
 #include <linux/vhost.h>
 
 #include "qemu/atomic.h"
@@ -64,6 +66,7 @@ vu_request_to_string(int req)
         REQ(VHOST_USER_IOTLB_MSG),
         REQ(VHOST_USER_SET_VRING_ENDIAN),
         REQ(VHOST_USER_POSTCOPY_ADVISE),
+        REQ(VHOST_USER_POSTCOPY_LISTEN),
         REQ(VHOST_USER_MAX),
     };
 #undef REQ
@@ -802,6 +805,22 @@ out:
 }
 
 static bool
+vu_set_postcopy_listen(VuDev *dev, VhostUserMsg *vmsg)
+{
+    vmsg->payload.u64 = -1;
+    vmsg->size = sizeof(vmsg->payload.u64);
+
+    if (dev->nregions) {
+        vu_panic(dev, "Regions already registered at postcopy-listen");
+        return true;
+    }
+    dev->postcopy_listening = true;
+
+    vmsg->flags = VHOST_USER_VERSION |  VHOST_USER_REPLY_MASK;
+    vmsg->payload.u64 = 0; /* Success */
+    return true;
+}
+static bool
 vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
 {
     int do_reply = 0;
@@ -868,6 +887,8 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
         break;
     case VHOST_USER_POSTCOPY_ADVISE:
         return vu_set_postcopy_advise(dev, vmsg);
+    case VHOST_USER_POSTCOPY_LISTEN:
+        return vu_set_postcopy_listen(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 3e8efdd919..29c11ba56c 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -67,6 +67,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_IOTLB_MSG        = 22,
     VHOST_USER_SET_VRING_ENDIAN = 23,
     VHOST_USER_POSTCOPY_ADVISE  = 24,
+    VHOST_USER_POSTCOPY_LISTEN  = 25,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -237,6 +238,7 @@ struct VuDev {
 
     /* Postcopy data */
     int postcopy_ufd;
+    bool postcopy_listening;
 };
 
 typedef struct VuVirtqElement {
diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index dad2a1b343..73c3dd74db 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -615,6 +615,12 @@ Master message types
       the slave must open a userfaultfd for later use.
       Note that at this stage the migration is still in precopy mode.
 
+ * VHOST_USER_POSTCOPY_LISTEN
+      Id: 25
+      Master payload: N/A
+
+      Master advises slave that a transition to postcopy mode has happened.
+
 Slave message types
 -------------------
 
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 775461ae98..f736c7c84f 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -1,5 +1,8 @@
 # See docs/devel/tracing.txt for syntax documentation.
 
+# hw/virtio/vhost-user.c
+vhost_user_postcopy_listen(void) ""
+
 # hw/virtio/virtio.c
 virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned out_num) "elem %p size %zd in_num %u out_num %u"
 virtqueue_fill(void *vq, const void *elem, unsigned int len, unsigned int idx) "vq %p elem %p len %u idx %u"
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index b7898f8939..9178271ab2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -69,6 +69,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_IOTLB_MSG = 22,
     VHOST_USER_SET_VRING_ENDIAN = 23,
     VHOST_USER_POSTCOPY_ADVISE  = 24,
+    VHOST_USER_POSTCOPY_LISTEN  = 25,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -788,6 +789,32 @@ static int vhost_user_postcopy_advise(struct vhost_dev *dev, Error **errp)
     return 0;
 }
 
+/*
+ * Called at the switch to postcopy on reception of the 'listen' command.
+ */
+static int vhost_user_postcopy_listen(struct vhost_dev *dev, Error **errp)
+{
+    int ret;
+    VhostUserMsg msg = {
+        .request = VHOST_USER_POSTCOPY_LISTEN,
+        .flags = VHOST_USER_VERSION | VHOST_USER_NEED_REPLY_MASK,
+    };
+
+    trace_vhost_user_postcopy_listen();
+    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
+        error_setg(errp, "Failed to send postcopy_listen to vhost");
+        return -1;
+    }
+
+    ret = process_message_reply(dev, &msg);
+    if (ret) {
+        error_setg(errp, "Failed to receive reply to postcopy_listen");
+        return ret;
+    }
+
+    return 0;
+}
+
 static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
                                         void *opaque)
 {
@@ -810,6 +837,9 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
     case POSTCOPY_NOTIFY_INBOUND_ADVISE:
         return vhost_user_postcopy_advise(dev, pnd->errp);
 
+    case POSTCOPY_NOTIFY_INBOUND_LISTEN:
+        return vhost_user_postcopy_listen(dev, pnd->errp);
+
     default:
         /* We ignore notifications we don't know */
         break;
diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
index 28c216cc7a..873c147b68 100644
--- a/migration/postcopy-ram.h
+++ b/migration/postcopy-ram.h
@@ -129,6 +129,7 @@ void postcopy_infrastructure_init(void);
 enum PostcopyNotifyReason {
     POSTCOPY_NOTIFY_PROBE = 0,
     POSTCOPY_NOTIFY_INBOUND_ADVISE,
+    POSTCOPY_NOTIFY_INBOUND_LISTEN,
 };
 
 struct PostcopyNotifyData {
diff --git a/migration/savevm.c b/migration/savevm.c
index d35911731d..72f084e10d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1557,6 +1557,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
 {
     PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_LISTENING);
     trace_loadvm_postcopy_handle_listen();
+    Error *local_err = NULL;
+
     if (ps != POSTCOPY_INCOMING_ADVISE && ps != POSTCOPY_INCOMING_DISCARD) {
         error_report("CMD_POSTCOPY_LISTEN in wrong postcopy state (%d)", ps);
         return -1;
@@ -1578,6 +1580,11 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
         return -1;
     }
 
+    if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_LISTEN, &local_err)) {
+        error_report_err(local_err);
+        return -1;
+    }
+
     if (mis->have_listen_thread) {
         error_report("CMD_POSTCOPY_RAM_LISTEN already has a listen thread");
         return -1;
-- 
2.13.5