According to AMD’s latest security white paper, the use of IBPB is the company’s recommended measures for the Ghost 2 variant:
While its CPUs do support other methods of controlling the behavior of the branch predictor in response to past predictions (a special bit indicating Indirect Branch Restricted Spectulation, or IBRS) and in response to sibling threads on a processor (a bit indicating Single Thread Indirect Branch Predictor, or STIBP), AMD does not recommend employing those methods as “performant” mitigations against Spectre.
Of course, just downloading system operating system updates is not enough to protect the affected system. AMD stated that product users should check the OEM or motherboard manufacturer’s website for updates to mitigate the impact of the vulnerability.
We were able to fully patch one of our Ryzen systems this way, and quick benchmarks suggest that any performance impact is minor—about 3% or so for the Javascript benchmarks we use as a gauge of day-to-day performance impacts.
It should be noted that this month’s “Tuesday Patch” does not mean that Microsoft has brought more Intel microcode updates, which may remain the same as in the past few weeks. Users of older CPUs, such as Skylake, still have to wait for OEMs or motherboard makers to issue firmware updates.
Source: TechReport
