For a single VM, you divide data point A (number of virtual processors supporting the VM) by data point B (# of cores [HTT off] or threads [HTT on] per physical processor) to calculate the number of Processor licenses required for any SQL Server edition(s) that will be licensed. If the result is not a whole number, then you round up to the next whole number
This example server has two quad-core processors supporting one VM running SQL Server. Hyper-threading is off, so each virtual processor is the equivalent of one core
Note: If both of the physical processors are licensed for SQL Server Enterprise, then the software may be run on as many VMs as the hardware and operating system will support