CP-17481: Add upgrade logic for new Host.control_domain

This needs to be done before the "hi-level" database upgrade because the
code to ensure the VM record for dom0 exists is in the dbsync logic
which is called as part of starting the database engine. This all
happens before the DB upgrade, and therefore, the dbsync logic tries to
create an additional dom0 record because it does not have the
Host.control_domain link.

This patch adds the Host.control_domain link during the dbsync if it
finds a VM with the CONTROL_DOMAIN_UUID from the Xensource_inventory.

Signed-off-by: Si Beaumont <[email protected]>

Author: simonjbeaumont

ocaml/xapi/create_misc.ml

@@ -134,11 +134,21 @@ let (+++) = Int64.add
 (** It updates existing records if they are found, or else creates new *)
 (** records for any records that are missing.                          *)
 let rec ensure_domain_zero_records ~__context ~host (host_info: host_info) : unit =
+	maybe_upgrade_domain_zero_record ~__context ~host host_info;
 	let domain_zero_ref = ensure_domain_zero_record ~__context host_info in
 	ensure_domain_zero_console_record ~__context ~domain_zero_ref;
 	ensure_domain_zero_guest_metrics_record ~__context ~domain_zero_ref host_info;
-	ensure_domain_zero_shadow_record ~__context ~domain_zero_ref;
-	Db.Host.set_control_domain ~__context ~self:host ~value:domain_zero_ref
+	ensure_domain_zero_shadow_record ~__context ~domain_zero_ref
+
+and maybe_upgrade_domain_zero_record ~__context ~host (host_info: host_info) =
+	try
+		let control_domain = Db.VM.get_by_uuid ~__context ~uuid:host_info.dom0_uuid in
+		if Db.Host.get_control_domain ~__context ~self:host = Ref.null then begin
+			debug "Setting control domain for host %s to %s"
+				(Ref.string_of host) (Ref.string_of control_domain);
+			Db.Host.set_control_domain ~__context ~self:host ~value:control_domain;
+		end
+	with Db_exn.Read_missing_uuid(_) -> ()
 
 and ensure_domain_zero_record ~__context (host_info: host_info): [`VM] Ref.t =
 	let ref_lookup () = Helpers.get_domain_zero ~__context in
@@ -226,6 +236,7 @@ and create_domain_zero_record ~__context ~domain_zero_ref (host_info: host_info)
 		~hardware_platform_version:0L
 		~has_vendor_device:false
 	;
+	Db.Host.set_control_domain ~__context ~self:localhost ~value:domain_zero_ref;
 	Xapi_vm_helpers.update_memory_overhead ~__context ~vm:domain_zero_ref
 
 and create_domain_zero_console_record_with_protocol ~__context ~domain_zero_ref ~dom0_console_protocol =