Phoronix published a review on the NVIDIA Gaming Performance Minimally Impacted By KPTI Patches
A quote from the article:
Earlier this week when news was still emerging on the "Intel CPU bug" now known as Spectre and Meltdown I ran some Radeon gaming tests with the preliminary Linux kernel patches providing Kernel Page Table Isolation (KPTI) support. Contrary to the hysteria, the gaming performance was minimally impacted with those open-source Radeon driver tests while today are some tests using the latest NVIDIA driver paired with a KPTI-enabled kernel.NVIDIA Gaming Performance Minimally Impacted By KPTI Patches @ Phoronix