Re: [Qemu-devel] [PATCH 00/21] Kemari for KVM 0.2

Paul Brook
2010-11-27T11:21:06Z

> One question I have about Kemari is whether it adds new constraints to
> the QEMU codebase? Fault tolerance seems like a cross-cutting concern
> - everyone writing device emulation or core QEMU code may need to be
> aware of new constraints. For example, "you are not allowed to
> release I/O operations to the outside world directly, instead you need
> to go through Kemari code which makes I/O transactional and
> communicates with the passive host". You have converted e1000,
> virtio-net, and virtio-blk. How do we make sure new devices that are
> merged into qemu.git don't break Kemari? How do we go about
> supporting the existing hw/* devices?

IMO anything that requires devices to act differently is wrong. All external
IO already goes though a common API (e.g. qemu_send_packet). You should be
putting your transaction code there, not hacking individual devices.

Paul