With Meltdown and Spectre now unveiled and out in the wild, focus has shifted on how to contain the problems they represent and not tank CPU performance in the process. Different vendors have released their own statements — Intel is hit the hardest by Meltdown, ARM has some limited vulnerability, and so on — but AMD has stayed pretty quiet, apart from its initial statement last week.
Today, the company published an update to its previous guidance, with more specific information. AMD continues to state it’s immune to Meltdown (Variant 3), the attack that specifically hits Intel the hardest, writing: “We believe AMD processors are not susceptible due to our use of privilege level protections within paging architecture and no mitigation is required.”
Variant 1 (Bounds Check Bypass, Spectre) is a problem AMD believes can be mitigated through software. This appears to be the patch that broke AMD systems; AMD says, “We are working closely with them [Microsoft] to correct an issue that paused the distribution of patches for some older AMD processors (AMD Opteron, Athlon and AMD Turion X2 Ultra families) earlier this week.”
Socket A bringing it back — anybody got some scotch tape and a pencil?
When MS and AMD referred to these bugs as affecting old chips, they weren’t kidding. Assuming AMD properly gave its own full brand names in each case, as they did with the Turion X2 Ultra, AMD’s Athlon is over a decade old, as is the original Opteron brand. These references could conceivably refer to newer cores, but even the Turion X2 Ultra turns 10 this year. Owners of Ryzen or even Piledriver-derived hardware don’t seem to have much to worry about.
As for Variant 2 (Branch Target Injection, the variant MS believes has the greatest chance of harming performance), AMD continues to believe the company’s architecture makes it difficult to exploit. AMD is distributing microcode updates and MS has OS patches to coming to make this issue harder to leverage for system attacks. Once again, no performance impact information has been published.
AMD’s overall position in this statement is consistent with its previous guidance on January 3rd. The company stated then that vulnerability to Variant 2 had not yet been demonstrated on an AMD system. The company’s new language, which states that Variant 2 is “difficult” to exploit, represents a departure from its previous message. But with no context for how easy or difficult the exploit might be, we can’t gauge the size of the shift or the new relative risk.