A longer history would start with IBM mainframes. More recently, IBM Ultravisor shipped in OpenPower firmware, mediating KVM VMs, https://www.youtube.com/watch?v=6qjrqn3ug0g & https://github.com/open-power/ultravisor

2018 video by Ian Pratt covers Xen, uXen and AX (2005-2015), https://news.ycombinator.com/item?id=44135977#44141164. Citrix acquired XenSource. Pratt left to work at Bromium, acquired by HP (which previously acquired BIOS company from Bromium co-founder). The former CTO of XenSource co-founded Qumranet (KVM), acquired by RedHat.

AWS began with Xen, then migrated to a subset of KVM. Nitro used Arm hardware to virtualize I/O (storage, network) paths, leaving KVM responsible for x86 CPU and memory virtualization, https://www.youtube.com/watch?v=e8DVmwj3OEs & https://news.ycombinator.com/item?id=24515019#24516523. Parallels could be drawn to the Apple T2 enclave (Arm) coprocessor being used for disk encryption on x86 Apple Macbooks.

Under the "Confidential Computing" umbrella, Intel has TDX and a new (closed?) hypervisor on servers, using SGX and new hardware privilege levels.

Apple recently added Secure eXclaves to iOS, and Apple Silicon hardware supports nested virtualization, which is what Google pKVM uses on Pixel (and upcoming ChromeOS?) devices, https://news.ycombinator.com/item?id=43314657

For production code, pKVM deserves attention because it's open (upstreamed to mainline Linux), exists in the real world (Pixel phones), stands in stark contrast to Apple's neutered iPads and has the potential to improve upon TrustZone security, https://news.ycombinator.com/item?id=41523758.

Finally, to bring this thread back to Barrelfish, Google OpenTitan open silicon root of trust (OCP servers, Chromebooks) is partly under Pulp Platform research, alongside Snitch (descended from Barrelfish research) open hardware from ETH Zurich. So progress is being made in both mainstream-compatible systems software and greenfield hardware cores.

(hopefully readers can correct any errors or gaps above)