CA-364138 log when about to stop varstored and varstore-guard

For debugging lost FDs in varstore-guard, log when whe call it to stop
serving a domain.

Signed-off-by: Christian Lindig <christian.lindig@citrix.com>

ocaml/xenopsd/lib/xenops_sandbox.ml

@@ -146,6 +146,7 @@ module Varstore_guard = struct
  let stop dbg ~domid ~vm_uuid =
  let chroot = varstored_chroot ~domid ~vm_uuid in
  if Sys.file_exists chroot.root then (
+ D.debug "About to stop varstored for %d (%s) %s" domid vm_uuid __LOC__ ;
  let gid = chroot.Chroot.gid in
  let absolute_socket_path =
  Chroot.absolute_path_outside chroot socket_path
@@ -155,5 +156,7 @@ module Varstore_guard = struct
  Varstore_privileged_client.Client.destroy dbg gid absolute_socket_path
  ) ;
  Chroot.destroy chroot
- )
+ ) else
+ D.warn "Can't stop varstored for %d (%s): %s does not exist" domid vm_uuid
+ chroot.root
 end

ocaml/xenopsd/xc/device.ml

@@ -2837,10 +2837,11 @@ module Dm_Common = struct
  in
  let stop_vgpu () = Vgpu.stop ~xs domid in
  let stop_varstored () =
+ let vm_uuid = Xenops_helpers.uuid_of_domid ~xs domid |> Uuidm.to_string in
+ debug "About to stop varstored for domain %d (%s)" domid vm_uuid ;
  Varstored.stop ~xs domid ;
  let dbg = Printf.sprintf "stop domid %d" domid in
- Xenops_sandbox.Varstore_guard.stop dbg ~domid
- ~vm_uuid:(Uuidm.to_string (Xenops_helpers.uuid_of_domid ~xs domid))
+ Xenops_sandbox.Varstore_guard.stop dbg ~domid ~vm_uuid
  in
  stop_vgpu () ; stop_varstored () ; stop_qemu ()