in our latest server with 2 x Epyc 7513, Ubuntu 18.04, and Kernel 5.4.0, the system correctly detects 64 total cores, but only 64 threads (instead of 128). In our older servers with 2 x Epyc 7452, everything works fine, and 128 threads are detected.
Does anybody know how to solve this issue?
lscpu command will show you if SMT is enabled or not - "Thread(s) per core: 1". If threads per core is 1 then you can enable it in BIOS settings.