This patch is part of a patchset that isn’t merged yet. The patchset adds 29% (with PCID) or > 50% (without PCID) overhead to syscalls on Intel processors.
Overall, this has between 0.28% (best case application with barely any syscalls) and > 50% (du, which does lots of syscalls) impact on performance on Intel processors.
> Nothing will happen since this patch will speed up AMD hardware, but leave Intel the same as before.
It doesn't speed up AMD hardware. Intel incurs a performance penalty (so it doesn't leave Intel the same as before), but that penalty doesn't make your AMD CPU magically go faster.
Overall, this has between 0.28% (best case application with barely any syscalls) and > 50% (du, which does lots of syscalls) impact on performance on Intel processors.