Intel has issued a new microcode update for mobile Skylake and mainstream desktop Skylake processors that gives operating systems the ability to protect against the Spectre flaw revealed earlier this year.
The company expects to also release updates OEM customers and industry partners for more platforms in the coming days. Beta microcode updates are also released so that Intel's partners have the opportunity to conduct testing before Intel moves them into production. Ultimately, these updates will be made available in most cases through OEM firmware updates.
Intel's first microcode update, developed late last year, was included in system firmware updates for machines with Broadwell, Haswell, Skylake, Kaby Lake, and Coffee Lake processors. But users subsequently discovered that the update was causing systems to crash and reboot.
In response, consumers were advised not to use the new microcode, and operating system features that leveraged the new capabilities were disabled.
After recommending customers not use its microcode fix for Broadwell and Haswell chips, Intel has issued a new microcode update for Skylake processors that gives operating systems the ability to protect against the Spectre flaw revealed earlier this year.
In short, Spectre is "persuading" a processor's branch predictor to make a specific bad prediction. This could be used to infer the value of data stored in memory. The updates are designed to give operating systems greater control over the branch predictor, enabling them to prevent one process from influencing the predictions made in another process.