Re: [PATCH v2 20/39] x86/bugs: Disable Retpoline when IBT

[Kees Cook]

On Thu, Feb 24, 2022 at 03:51:58PM +0100, Peter Zijlstra wrote:
> Retpoline and IBT are mutually exclusive. IBT relies on indirect
> branches (JMP/CALL *%reg) while retpoline avoids them by design.
> 
> Demote to LFENCE on IBT enabled hardware.

What's the expected perf impact of this?

-Kees

-- 
Kees Cook