Re: [Libguestfs] Improving supermin appliance startup time (lkvm/qboot)

I was looking at Clear Containers last week. [...] This is all very good analysis.

The issues that I had in brief were: (1) We could run kvmtool, perhaps by adding a new backend, but it seems a better idea to add the required features to qemu. Anything based on kvmtool wouldn't support qcow2 and the myriad other features of qemu (see also: https://rwmj.wordpress.com/2015/11/07/linux-kernel-library-backend-for-li...)

(2) On the kernel side, the Intel kernel contains lots of little hacks, and many baremetal CONFIG_* options are disabled. Hacks can be upstreamed once we massage them into shape. The real issue is keeping a single baremetal + virt kernel image, since separate kernel images would never fly with Fedora or RHEL. That means we cannot just disable slow drivers/subsystems by having an alternate kernel with lots of CONFIG_* options disabled, we need to address those problems properly. (3) DAX / NVDIMM / etc - love them. Not supported upstream (either kernel or qemu) yet. (4) Passthrough (eg 9p) filesystems. You touched on that above. Red Hat doesn't much like 9pfs for several reasons, yet we also don't have a plausible alternative at the moment. This is mainly a problem for running fast Docker containers, rather than libguestfs though.