...

Important note: Patches may impact performance, especially on servers and systems with already high load.  Reduced performance on Intel-based Microsoft Windows, MacOS, or Linux servers may be experienced as the operating systems are patched to close the security hole.  One projections puts this at a performance reduction between 17% and 23%. So far, real life testing on Linux suggestions < 10%.

How to Detect Vulnerability

Tenable

• TBD but will require authenticated or agent based scan
  

Microsoft

• Microsoft powershell script:  https://support.microsoft.com/en-hk/help/4073119/protect-against-speculative-execution-side-channel-vulnerabilities-in

Summary Articles and Useful Links

...