Does the AMD 5950X CPU support the INVPCID instruction? My impression is that AMD CPUs do not have the INVPCID instruction.
Perhaps you can verify this through HWinfo64 or through a bootable Linux USB in the /proc/cpuinfo
The INVPCID was introduced in Intel CPUs in the Haswell generation. It is used to INValidate TLB entries belonging to a specific Process Context IDentifier in the TLB and thus avoiding clearing the entire cache which will have entries belonging to other PCIDs.
The absence of the INVPCID could severely affect performance in I/O intensive workloads (not just VMs, but probably VMs get hit with a double whammy) as the TLB cache will be flushed when an application needs to switch context to I/O operation.