I have two machines running Archlinux with x2goserver running from arch repository packages that both exhibit abnormally high CPU usage in ksoftirqd/x (where x=the cpu core #).  Here is an example top output showing the usage while idle - ksoftirqd is always the top user of CPU when the system is idle:

top - 13:27:42 up 27 days, 16:27,  8 users,  load average: 0.84, 0.63, 0.49
Tasks: 326 total,   1 running, 325 sleeping,   0 stopped,   0 zombie
%Cpu(s):   0.6/0.7     1[||                                                                                                  ]
GiB Mem : 26.9/15.574   [                                                                                                    ]
GiB Swap:  5.4/16.000   [                                                                                                    ]

  PID USER      PR  NI    VIRT    RES  %CPU %MEM     TIME+ S COMMAND
   45 root      20   0    0.0m   0.0m   4.0  0.0 478:55.34 S ksoftirqd/7
   65 root      20   0    0.0m   0.0m   2.6  0.0 417:08.28 S ksoftirqd/11
   25 root      20   0    0.0m   0.0m   2.0  0.0 109:05.16 S ksoftirqd/3
   60 root      20   0    0.0m   0.0m   2.0  0.0 523:14.28 S ksoftirqd/10
 9180 rettw     20   0 2663.9m 1.321g   2.0  8.5  16:08.16 S VBoxHeadless
   50 root      20   0    0.0m   0.0m   1.3  0.0 527:10.22 S ksoftirqd/8
 9236 rettw     20   0 1588.0m 371.6m   1.3  2.3   2:29.45 S VBoxHeadless
    3 root      20   0    0.0m   0.0m   0.7  0.0 392:21.72 S ksoftirqd/0
   30 root      20   0    0.0m   0.0m   0.7  0.0 133:12.11 S ksoftirqd/4
   55 root      20   0    0.0m   0.0m   0.7  0.0 463:32.57 S ksoftirqd/9
 1005 rettw     20   0 3058.8m  66.6m   0.7  0.4  29:58.26 S kwin
 8502 root      20   0   35.1m   3.7m   0.7  0.0   0:13.56 R top
30713 rettw     20   0  605.3m  22.2m   0.7  0.1   6:45.55 S konsole
    1 root      20   0   33.6m   4.1m   0.0  0.0   0:18.42 S systemd
    2 root      20   0    0.0m   0.0m   0.0  0.0   0:00.32 S kthreadd