Ugh...Did anyone actually read the article? AMD is affected too, as is ARM. You fell for the clickbait headline. This nothing more than another Specter V1 variant.
As far as performance, here's Redhat:
There was some confusion on that at first. The original researchers said they tried it on 2 AMD chips but they weren't vulnerable. AMD says they are not affected. Microsoft says AMD is not affected. The Linux kernel patch only applies to Intel CPUs. Redhat is the only one saying AMD is vulnerable despite having no patch that applies to AMD systems.
I think the confusion comes in because there were multiple attack vectors for this exploit to work. Intel CPUs, even with the most current mitigations were vulnerable to all of the listed attack vectors. AMD was immune to all of them except one on a hardware level. For the one vector that could work on AMD, the Spectre variant 1 mitigation that was applied way back when this all started closes that vulnerability. So as long as you are patched for AMD with the initial Spectre mitigation, you're good to go, which is probably why the attacks failed on AMD CPUs for the original researchers.
tl;dr: AMD is not vulnerable to the new attack, Intel CPUs are. Performance hit doesn't look like hardly anything except a ~5% hit in some throughput tests.