Red Hat SummitChapter 1. Overview of alt-java
Red Hat packages contain a mitigation for the SSB vulnerability in the form of a patch for the java binary. This patch disables an optimization present in x86-64 (Intel and AMD) processors. Disabling that optimization reduces the risk of kernel side-channel attacks, but also reduces CPU performance.
Since the patch reduces performance, it has been removed from the java launcher. A new binary alt-java is now available. From the January 2021 Critical Patch Update release (1.8.0 282.b08, 11.0.10.9) onwards, the alt-java binary is included in Red Hat build of OpenJDK 17 and Red Hat build of OpenJDK 11 GA RPM packages.
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