CP-45741 VCS support, adjust args for qemu, demu

Part of CP-44317, CP-44320 suporting NVidia VCS. Adjust args when we are
running a VCS (compute) vGPU when starting qemu and demu:

* don't pass -vgpu to qemu
* pass --noconsole to demu

Remove a redundant match in cmdline_of_disp.

Signed-off-by: Christian Lindig <[email protected]>

ocaml/xenopsd/xc/device.ml

@@ -2091,9 +2091,11 @@ module Dm_Common = struct
   let cmdline_of_disp ?domid info =
     let vga_type_opts x =
       let open Xenops_interface.Vgpu in
+      (* We can match on the implementation details to detect the VCS
+         case. Don't pass -vgpu for a compute vGPU. *)
       match x with
-      | Vgpu [{implementation= Nvidia _; _}] ->
-          ["-vgpu"]
+      | Vgpu ({implementation= Nvidia {vclass= Some "Compute"; _}; _} :: _) ->
+          [] (* don't pass flags for VCS (compute) vGPU *)
       | Vgpu ({implementation= Nvidia _; _} :: _) ->
           ["-vgpu"]
       | Vgpu [{implementation= GVT_g gvt_g; _}] ->

ocaml/xenopsd/xc/service.ml

@@ -412,6 +412,16 @@ module Vgpu = struct
     let pid_location = Pid.Xenstore pid_path
   end)
 
+  (** An NVidia Virtual Compute Service vGPU has a class attribute
+     "Compute". Recognise this here *)
+  let is_compute_vgpu vgpu =
+    let open Xenops_interface.Vgpu in
+    match vgpu with
+    | {implementation= Nvidia {vclass= Some "Compute"; _}; _} ->
+        true
+    | _ ->
+        false
+
   let vgpu_args_of_nvidia domid vcpus vgpus restore =
     let open Xenops_interface.Vgpu in
     let virtual_pci_address_compare vgpu1 vgpu2 =
@@ -504,7 +514,15 @@ module Vgpu = struct
       @ device_args
     in
     let fd_arg = if restore then ["--resume"] else [] in
-    List.concat [base_args; fd_arg]
+    (* support for NVidia VCS (compute) vGPUs *)
+    let no_console =
+      match List.for_all is_compute_vgpu vgpus with
+      | true ->
+          ["--noconsole"]
+      | false ->
+          []
+    in
+    List.concat [base_args; no_console; fd_arg]
 
   let state_path domid = Printf.sprintf "/local/domain/%d/vgpu/state" domid