Kernel tainted with value 512 when using Intel® Optane™ Persistent Memory 200 Series with 3rd Generation Intel Xeon Scalable processors running RHEL 8.2

Environment

• Intel® Optane™ Persistent Memory 200 Series (Code Name Barlow Pass)
• Intel 3rd Generation Xeon Scalable Performance processors (Code Name Ice Lake Server)
• Red Hat Enterprise Linux 8.2

Issue

Systems configured as described in the environment will emit a kernel tainted warning at boot time.

Resolution

The taint warning is spurious and can be ignored. HMAT functionality is fairly recent and in certain scenarios could define memory (EFI_MEMORY_SP, for example) in such a way that it would be seen as offline by the kernel, so it would not be assigned to a NUMA node. Since the memory is either offline or does not exist it shouldn't really be added to a NUMA node. The HMAT code in RHEL 8.2 complains about proper behavior (by setting taint) and it should not. RHEL 8.3 pulled in code changes that cause the improper complaining to stop.