Red Hat engineers are working to deal with Indirect Branch Restricted Speculation (IBRS) being too costly for mitigating Spectre V2 and Retbleed on older Intel Xeon Scalable processors. A new patch has been floated to disable IBRS when idle and is working out well at least for Red Hat Enterprise Linux 9 while isn’t clear yet if it will be accepted into the upstream kernel…

Source: Phoronix – Red Hat Aiming To Address IBRS Mitigation Still Being Too Costly On Performance