Gaming performance doesn't seem to be affected, at least on Linux. Ars Technica are suggesting that gaming-in-general is likely to be unaffected, for all intents and purposes.
Just watched the video posted above - "desktop users, particularly gamers, really have nothing to worry about."
This disappoints me, as I was hoping to use the vulnerabilities and their patches to justify buying a Ryzen 7 CPU and MoBo, which I can now no longer do without lying.
*edit*
The Register have a rather amusing analysis of Intel's recent press release on the issue. It made me giggle more than once.
Well while gamers might not be affected directly we will be affected indirectly since game servers are likely to take a hit.