[The Exiled]

Meltdown & Spectre: Misconceptions, Current Status, & Expert Interviews

Meltdown is generally agreed to be more severe, but limited to Intel, while Spectre has to do with a fundamental aspect of CPUs made in the past 20 years. They involve an important technique used by modern CPUs to increase efficiency, called “speculative execution,” which is allows a CPU to preemptively queue-up tasks it speculates will next occur. Sometimes, these cycles are wasted, as the actions never occur as predicted; however, most of the time, speculating on incoming jobs will greatly improve efficiency of the processor by preemptively computing the inbound instructions.

Meltdown is a really annoying flaw but it is fairly obvious what needs to be changed in hardware so I fully expect upcoming processors not to be susceptible. In the mean time, patches like Linux KPTI provide effective protection. With Spectre I would argue that all current hardware modifications are mere stop-gap solutions. I guess it will take some time and good old fashioned research to figure out the most efficient way of mitigating such attacks.