The NVIDIA 390 Driver Is Playing Nicely With Linux 4.15 Kernel
Earlier NVIDIA driver releases ran into compatibility issues with the Linux 4.15 interfaces following the merge window (not due to KPTI, as some other FUD previously passed around by others). But with last week's NVIDIA 390.12 beta it has been working fine atop the Linux 4.15 Git kernel, including when Kernel Page Table Isolation is enabled for Meltdown prevention. (Retpoline support has yet to be mainlined, haven't tested the NVIDIA driver there yet to formally confirm if any breakage may happen.)
I've been running NVIDIA 390.12 on Linux 4.15 Git as of this week with multiple Pascal and Maxwell cards with no issues to speak of yet, which is good if you're wanting to run the newest kernel code, such as for the many new Linux 4.15 kernel features.
Besides fixing the vRAM leakage, adding official support for newer Pascal cards, and providing various fixes, the NVIDIA 390.12 driver (along with 384.111) are also helping safeguard against Spectre.
Within the next day or so will be the results of a large Radeon/NVIDIA comparison with Linux 4.15 and the latest respective drivers.