The Performance Impact Of AMD Changing Their Retpoline Method For Spectre V2

Made public this week was the Spectre-BHB / BHI vulnerability and while only Intel and Arm processors are currently believed to be impacted, in the course of that research the folks at VUSec discovered AMD's current Retpoline strategy for Spectre V2 mitigations is not adequate. This has led to a change in behavior for AMD processors and is already applied to the Linux kernel. Here is a look at what it means for desktop and server performance due to the change in return trampoline handling.