Red Hat's Spectre remediation currently requires new microcode for a complete fix, which leaves most x86 processors vulnerable as they lack this update. Oracle has released new retpoline kernels that completely remediate Meltdown and Spectre on all compatible CPUs, which I show how to install and test on CentOS here.
The Red Hat community has patiently awaited a retpoline kernel
implementation that remediates CVE-2017-5715 (Spectre v2) and closes all
Meltdown and Spectre vulnerabilities that have captured headlines this