Question Regarding KABI stability and GA Kernel

[Seth Forshee]

On Sat, May 27, 2017 at 02:38:30AM +0530, sunita shah wrote:
> Hello Ubuntu Kernel Team,
> 
> I have a question regarding 16.04 Ubuntu Kernel and ABI compatibility. I
> recently ran into an issue while using "get_user_pages_locked" API. I have
> an out-of-tree kernel module which uses this API and was working fine on
> 16.04.0, however when I switched to 16.04.2 (desktop ISO, kernel version
> 4.8), I found that API signatures were changed and I had to fix that
> manually in the production environment.
> 
> My question is If I stick to 16.04.0/1 GA kernel version and never
> explicitly opt for HWE kernel, would Ubuntu ensure that all patch releases
> on GA kernel don't break the existing API surface? I understand that new
> APIs might be added, but I am more concerned about existing APIs being used
> by my module.

We don't ensure ABI stability. The usual solution for this is to use
DKMS to build the module separately for each installed kernel.

There's some documentation here, though I don't know whether it is up to
date.

 https://help.ubuntu.com/community/DKMS

Seth