[$] Avoiding retpolines with static calls

January 2018 was a sad time in the kernel community. The Meltdown andSpectre vulnerabilities had finally been disclosed, and the requiredworkarounds hurt kernel performance in a number of ways. One of thoseworkarounds - retpolines -continues to cause pain, with developers goingout of their way to avoid indirect calls, since they must now be implementedwith retpolines. In some cases, though, there may be a way to avoid retpolines and regain much of the lost performance;after a long gestation period, the "static calls" mechanism may finally benearing the point where it can be merged upstream.