Allow moving last PGPU out of GPU group with VGPUs

With the new API, it is perfectly reasonably to create VGPUs on GPU groups with
no pGPUs in them since vGPU -> pGPU allocation is done at VM start time. As
such we can loosen the requirements on moving the last pGPU out of a GPU group.

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

Author: simonjbeaumont

ocaml/idl/api_errors.ml

@@ -248,7 +248,6 @@ let event_from_token_parse_failure = "EVENT_FROM_TOKEN_PARSE_FAILURE"
 let session_not_registered = "SESSION_NOT_REGISTERED"
 
 let pgpu_in_use_by_vm = "PGPU_IN_USE_BY_VM"
-let pgpu_required_by_gpu_group = "PGPU_REQUIRED_BY_GPU_GROUP"
 let pgpu_not_compatible_with_gpu_group = "PGPU_NOT_COMPATIBLE_WITH_GPU_GROUP"
 let pgpu_insufficient_capacity_for_vgpu = "PGPU_INSUFFICIENT_CAPACITY_FOR_VGPU"
 let vgpu_type_not_enabled = "VGPU_TYPE_NOT_ENABLED"

ocaml/idl/datamodel.ml

@@ -544,8 +544,6 @@ let _ =
 
   error Api_errors.pgpu_in_use_by_vm ["VMs"]
     ~doc:"This PGPU is currently in use by running VMs." ();
-  error Api_errors.pgpu_required_by_gpu_group ["gpu_group"]
-    ~doc:"Moving this PGPU would leave unbacked VGPUs in the GPU group." ();
   error Api_errors.pgpu_not_compatible_with_gpu_group ["type"; "group_types"]
     ~doc:"PGPU type not compatible with destination group." ();
   error Api_errors.pgpu_insufficient_capacity_for_vgpu ["pgpu"; "vgpu"]

ocaml/xapi/xapi_pgpu.ml

@@ -110,18 +110,6 @@ let set_GPU_group ~__context ~self ~value =
 			raise (Api_errors.Server_error (Api_errors.pgpu_in_use_by_vm,
 				List.map Ref.string_of attached_vms));
 
-		(* Precondition: Moving PGPU from current group can't orphan VGPU *)
-		let src_g = Db.PGPU.get_GPU_group ~__context ~self in
-		if Db.is_valid_ref __context src_g then begin
-			let pgpu_is_singleton =
-				(List.length (Db.GPU_group.get_PGPUs ~__context ~self:src_g) = 1)
-			and pgpu_has_vgpus =
-				((Db.GPU_group.get_VGPUs ~__context ~self:src_g) <> []) in
-			if (pgpu_is_singleton && pgpu_has_vgpus) then
-				raise (Api_errors.Server_error
-					(Api_errors.pgpu_required_by_gpu_group, [Ref.string_of src_g]))
-		end;
-
 		let check_compatibility gpu_type group_types =
 			match group_types with
 			| [] -> true, [gpu_type]