The concept of using virtual machines was popular in the 1960s and 1970s in both the computing industry and academic research. In these early days of comput- ing, virtual machine monitors (VMMs) allowed multiple users, each running their own single-user operating system instance, to share the same costly mainframe hardware [Goldberg 1974]. Virtual machines lost popularity with the increased sophistication of multi-user operating systems, the rapid drop in hardware cost, and the corresponding proliferation of computers. By the 1980s, the industry had lost interest in virtualization and new computer architectures developed in the 1980s and 1990s did not include the necessary architectural support for virtualization.
  In our research work on system software for scalable multiprocessors, we discov- ered that using virtual machine monitors could solve, simply and elegantly, a number of hard system software problems by innovating in a layer below existing operating systems. The key observation from our Disco work [Bugnion et al. 1997] was that, while the high complexity of modern operating systems made innovation difficult, the relative simplicity of a virtual machine monitor and its position in the software stack provided a powerful foothold to address limitations of operating systems.

The obvious takeaway? Flexible software optimizations often beat hardware if exits are too heavy or inflexible. Makes me wonder: with modern nested virtualization and microarchitectural improvements, are we finally seeing hardware VMMs that consistently match or exceed software VMMs?

[1] https://pages.cs.wisc.edu/~remzi/Classes/838/Spring2013/Pape...