[PATCH v3 2/7] vhost-vsock: don't reset connections during CPR

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

Migration target with a vhost-vsock device in the .post_load() hook issues
VIRTIO_VSOCK_EVENT_TRANSPORT_RESET event to the guest.  This results into
the guest tearing down all its vsock connections.  That reset exists
because after a normal migration the cid may change.

However it's not true for CPR-style migration.  In this case cid remains
the same, and we want the connections to persist.  Thus, let's customize
the .post_load() hook to skip the common transport reset part in this case.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
---
 hw/virtio/vhost-vsock.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
index da244eb1657..cdc58d58790 100644
--- a/hw/virtio/vhost-vsock.c
+++ b/hw/virtio/vhost-vsock.c
@@ -20,6 +20,7 @@
 #include "hw/core/qdev-properties.h"
 #include "hw/virtio/vhost-vsock.h"
 #include "monitor/monitor.h"
+#include "migration/cpr.h"
 
 static void vhost_vsock_get_config(VirtIODevice *vdev, uint8_t *config)
 {
@@ -108,6 +109,20 @@ static uint64_t vhost_vsock_get_features(VirtIODevice *vdev,
     return vhost_vsock_common_get_features(vdev, requested_features, errp);
 }
 
+static int vhost_vsock_post_load(void *opaque, int version_id)
+{
+    /*
+     * Only reset vsock connections for non-CPR migration.  For CPR the
+     * guest cid is unchanged, and the cid-change reset would otherwise
+     * tear the vsock connections down.
+     */
+    if (cpr_is_incoming()) {
+        return 0;
+    }
+
+    return vhost_vsock_common_post_load(opaque, version_id);
+}
+
 static const VMStateDescription vmstate_virtio_vhost_vsock = {
     .name = "virtio-vhost_vsock",
     .minimum_version_id = VHOST_VSOCK_SAVEVM_VERSION,
@@ -117,7 +132,7 @@ static const VMStateDescription vmstate_virtio_vhost_vsock = {
         VMSTATE_END_OF_LIST()
     },
     .pre_save = vhost_vsock_common_pre_save,
-    .post_load = vhost_vsock_common_post_load,
+    .post_load = vhost_vsock_post_load,
 };
 
 static void vhost_vsock_device_realize(DeviceState *dev, Error **errp)
-- 
2.47.1