I don't get the distinction between type 1 and type 2.
E.g. xen is type 1 and KVM is type 2. But at the end of the day it's a Linux kernel in both cases that runs the virtual machines, so what's the point of distinction?
>>tryauu+(OP)
It's what runs above the vms that is the distinction. For xen it has its own kernel instead of running Linux as the hypervisor and host system. Xen still uses Linux typically as the domain zero as it calls it for doing control and setup but it doesn't necessarily have full access to all the hardware on its own.
>>tryauu+(OP)
It's about reducing the size and attack surface of the most-privileged code which runs in the system, e.g. moving code out of the kernel, making hypervisor/VMM smaller, nested VMs, hardware enclaves. This video covers some of the changes over the last decade, including Xen and Bromium, https://youtube.com/watch?v=bNVe2y34dnM
>>tryauu+FW1
Completely it's own from scratch. It's a very simple, relative to full Linux or other OS, kernel/hypervisor. It's built to load what it calls the Dom0 system, which it gives a communication channel to to start up other virtual systems that it calls DomU. This in theory lets you use any OS as the Dom0 for initializing everything (Linux, *BSD, even Windows I think) as long as there's some kind of support for that communications channel to tell the Xen kernel to start up another system.