[Someone]

Also, for the way most modern CPUs are used: how do you task switch? If the hardware is large enough, you can deploy multiple configurations at a time, but does software support that? Is is possible to have relocatable configurations?

In theory, you could even page out code, but I guess the speed of that will be slow. Also, paging in probably would be challenging because the logical units aren’t uniform (if only because not all of them will be connected to external wires)

[varispeed]

This can be used with a client-server model, that is if there are enough free cells and I/O available on FPGA it could let it install the configuration and then any application could communicate with it concurrently, maybe with some basic auth.

[Someone]

But from what I understand of FPGAs, fragmentation would be a serious issue. You may have the free cells and I/O you need to implement some circuit, but if they’re dispersed over your FPGA or even connected, but in the wrong shape for the circuit you’re building, that’s useless.

An enormous crossbar could solve that, but I would think that would be way too costly, if practically possible at all.

[rjsw]

You can reconfigure just part of the FPGA, it isn't used all that often though.