@gordon - laptop or desktop?
The kernel team did something with acpi a while back so now all these acpi errors and/or warnings show up when booting. I get about 6-7 of them any time I boot my laptop and never found a fix.
The 4.4 LTS kernel doesn't have these changes so I use it as my backup kernel.
Honestly said, though, I have used the 4.14 and 4.4 kernels enough now to know there are no performance degradations between the two. My battery life and temps are essentially the same.
If you're really motivated, you can find some acpi conversations at the kernel.org site. I read through a few but it was pretty much like reading Sumerian cuneiform.