Phoronix published A Look At The MDS Cost On Xeon, EPYC & Xeon Total Impact Of Affected CPU Vulnerabilities A quote from the article:

This weekend I posted a number of benchmarks looking at the performance impact of the new MDS/Zombieload vulnerabilities that also included a look at the overall cost of Spectre/Meltdown/L1TF/MDS on Intel desktop CPUs and AMD CPUs (Spectre). In this article are similar benchmarks but turning the attention now to Intel Xeon hardware and also comparing those total mitigation costs against AMD EPYC with its Spectre mitigations.

 A Look At The MDS Cost On Xeon, EPYC & Xeon Total Impact Of Affected CPU Vulnerabilities