This question is about SQL Server Licencing and licencing for Maximum Virtualisation.
I'm curious about the licence position for this scenario.
You have one Hyper-V host (HOST1) with say 48 cores all core licenced with Enterprise Core and covered by SA. You can run an unlimited number of VMs.
You have a second Hyper-V host (HOST2) in a cluster with HOST1 which also with 48 cores, it is in the same server farm. HOST2 does not have SQL Server core licences. HOST2 runs passive VMs with passive secondary SQL Server instances that are nodes in AG, and possibly FCI instances supporting VMs hosted on HOST1. My current position is these VMs on host two are covered by SA and the benefits that bestow around passive instances for HA and DR.
If HOST1 died a nasty death, the AGs and FCI would failover to VMs on HOST2, and the SA failover HA benefits cover this. The standalone instances configured for High Availability in Hyper-V and would be restarted on HOST2 two in the event of HOST1 becoming unavailable. We could use the license mobility benefit to reassign the licenses to this second host, and we would be covered.
If those standalone VMs on HOST1 were capable of Live Migrating to HOST2, which would only be done for doing things like patching the HOSTS, Failover AGs and FCIs to HOST2 Live Migrate standalone VMs to HOST2. Patch HOST1 and Failback to HOST1 etc. The VMs can automatically Live Migrate to HOST2 I think that would change the position and HOST2 would need to be licenced as well but I am not 100% sure and interested in others opinions. Please do share.