CP-22500: support clean suspend,shutdown etc for HVM Linux using upstream qemu

The original qemu-trad patch added as part of CP-9364 was split into two:

- a small upstream qemu patch that implements the xen platform io-port 0x10 and
collects the product-num and build-num for the PV driver, and exposes them via
the new query-xen-platform-pv-driver-info QMP command, see qemu.pg PR 34:
  . CP-23471: Expose product number and build number of XEN PV driver

- this xenopsd patch, which collects product-num and build-num for the PV
driver using the QMP command above, and using the original algorithm in
qemu-trad, decides if the PV driver belongs to a HVM Linux guest. In this case,
it writes to xenstore as qemu-trad would have done, see qemu-trad.pg patches:
  . CP-9364: write feature-flags to xenstore when HVM guest stops using
    emulated devices
  . CP-9364: xapi expects data/updated to exist

This patch keeps the same behaviour present in the original qemu-trad patch,
in order to maintain the the support for clean suspend, shutdown etc for the
same set of HVM Linux guests.

Signed-off-by: Marcus Granado <[email protected]>

Author: mg12ctx

xc/device.ml

@@ -1912,6 +1912,29 @@ let stop ~xs ~qemu_domid domid  =
     stop_vgpu ();
     stop_qemu ()
 
+let is_hvm_linux domid =
+	let _XEN_IOPORT_LINUX_PRODNUM = 3 in (* from Linux include/xen/platform_pci.h *)
+	let error x = error "%s" x; Result.Error x in
+	try
+		let open Qmp in
+		match qmp_write_and_read domid (Command (None, Query_xen_platform_pv_driver_info)) with
+		| Some (Success (None, Xen_platform_pv_driver_info { product_num; build_num })) ->
+			Result.Ok ((product_num = _XEN_IOPORT_LINUX_PRODNUM) && (build_num <= 0xff))
+		| Some x ->
+			error (Printf.sprintf "Unexpected QMP response: %s" (Qmp.string_of_message x))
+		| None -> error "No QMP response for Query_xen_platform_pv_driver_info"
+	with e ->
+		error (Printf.sprintf "Exception attempting to obtain Linux product_id and build_number: %s" (Printexc.to_string e))
+
+let maybe_write_pv_feature_flags ~xs domid =
+	if is_upstream_qemu domid then
+	match is_hvm_linux domid with
+	| Result.Ok true ->
+		let write_local_domain prefix x = xs.Xs.write (Printf.sprintf "/local/domain/%d/%s%s" domid prefix x) "1" in
+		List.iter (write_local_domain "control/feature-") ["suspend"; "shutdown"; "vcpu-hotplug"];
+		List.iter (write_local_domain "data/") ["updated"]
+	| _ -> ()
+
 end (* End of module Dm *)
 
 let get_vnc_port ~xs domid = 

xc/device.mli

@@ -233,6 +233,8 @@ sig
 	val suspend : Xenops_task.task_handle -> xs:Xenstore.Xs.xsh -> qemu_domid:int -> Xenctrl.domid -> unit
 	val resume : Xenops_task.task_handle -> xs:Xenstore.Xs.xsh -> qemu_domid:int -> Xenctrl.domid -> unit
 	val stop : xs:Xenstore.Xs.xsh -> qemu_domid:int -> Xenctrl.domid -> unit
+
+	val maybe_write_pv_feature_flags : xs:Xenstore.Xs.xsh -> Xenctrl.domid -> unit
 end
 
 val get_vnc_port : xs:Xenstore.Xs.xsh -> Xenctrl.domid -> int option

xc/xenops_server_xen.ml

@@ -2763,6 +2763,7 @@ module Actions = struct
 							let non_persistent = { non_persistent with VmExtra.pv_drivers_detected = true } in
 							debug "VM = %s; found PV driver evidence on %s (value = %s)" vm path value;
 							DB.write vm { VmExtra.persistent; non_persistent };
+							Device.Dm.maybe_write_pv_feature_flags ~xs domid;
 							Updates.add (Dynamic.Vm vm) internal_updates
 						end
 					with Xs_protocol.Enoent _ ->