SQL Server uses too much CPU
Issue is the following.

Let a Hyper-V VM is configured with high startup memory (like 10240MB), and dynamic memory limits active and are like 512-10240 range.

VM starts up with full amount of RAM available. Short after load the host reclaims excess memory from the VM. At the same moment SQL Server process starts to create that unexplainable CPU load.

It doesn't happens though, if startup memory set to 512MB.