Re: [libvirt] RFC: libvirt support for QEMU live patching

On Fri, Sep 15, 2017 at 09:18:18AM +0100, Daniel P. Berrange wrote: > On Fri, Sep 15, 2017 at 01:27:31PM +0530, Madhu Pavan wrote:

> It isn't possible to make it work correctly in the general case, because > both QEMU processes want to own the same files on disk. eg both might want > to listen on a UNIX socket /foo/bar, but only one can do this. If you let > the new QEMU delete the original QEMU's sockets, then you either break or > delay incoming connections during the migration time, and you make it > impossible to roll back on failure, or both. This kind of thing is not > something that's acceptable for the usage scenerio described, which would > need to be bulletproof to be usable in production. > Can't we utilize namespaces for this? Lot of the things could be separated, so we could fire up a new VM that's "containerized" like this, migrate to it and then fire up a new one and migrate back. If the first migration fails then we can still fallback. If it does not, then the second one "should" not either.