"If this were true, and an issue, FPGAs would also be completely unusable in production."
BOOM! And kernels. And ASIC's. And so on. Yet, we have tools to debug all of them. But unikernels? Better off trying to build a quantum computer than something that difficult...
It's not the same as using something like DTrace on a live system, but he's describing it as though eliminating the flexibility implies some sort of event horizon.
This also bothered me...
virtualizing at the hardware layer carries with it an inexorable performance tax
Hardware has been adding a lot of virtualization support over the last decade, and it's generally been a net performance gain as far as I'm aware. I could see things like IO scheduling potentially being an issue. Although, IO performance on top of operating systems in general does not particularly inspire confidence.
Next time you see that, point out that the hardware is itself basically virtualized to monolithic OS's with microcode, shared I/O, and multiplexed buses. A version could work for unikernels if that worked for UNIX. Performance issues come more from how it's applied than the concept itself.
I think you guys might find Arrakis interesting: https://arrakis.cs.washington.edu/ it won Best Paper at OSDI '14 and demonstrates a possible way to better use things like virtio.
BOOM! And kernels. And ASIC's. And so on. Yet, we have tools to debug all of them. But unikernels? Better off trying to build a quantum computer than something that difficult...