qemu-system-i386: -mem-path not supported with Xen when try to use memory-backend-memfd to share the memory with external processes on qemu-xen stable-4.16

[Trigger Huang <trigger.huang@xxxxxxxxx>]

Hello,

The QEMU Documentation suggests to use memory-backend-memfd to share the memory with external processes, so I  add the following patch to libxl__build_device_model_args_new() @ tools/libs/light/libxl_dm.c

+               flexarray_append_pair(dm_args, "-object", "memory-backend-memfd,id=mem1,size=4G");
+               flexarray_append_pair(dm_args, "-machine", "memory-backend=mem1");

However, I always got error 'qemu-system-i386: -mem-path not supported with Xen'

After check the qemu-xen source, the error is from 'qemu_ram_alloc_from_fd() @ softmmu/physmem.c

    if (xen_enabled()) {
        error_setg(errp, "-mem-path not supported with Xen");
        return NULL;
    }

So, any suggestions on how to enable  -mem-path on Xen?

Thanks,

Trigger