Database/Firmware, BMC & network fabric
AMD Ryzen with AGESA microcode - FMA3 instruction sequence hang: A long series of FMA3 instructions hangs the system
Impact
A long series of FMA3 instructions hangs the system. FMA3 is the fused multiply-add path that every dense linear-algebra kernel hammers, so on an ML host this is not an exotic instruction sequence - it is the normal workload. An unprivileged tenant running a numerical benchmark can hang the node, deliberately or by accident.
Who can reach it
Local, unprivileged. Reachable from any container running numerical code.
What to do
Fixed by an AGESA microcode update from 2017 onward, delivered as an OEM BIOS package. Client Ryzen silicon rather than EPYC, so on a server fleet this is mostly a non-issue - verify your SKUs before spending a window on it.
References
This entry is curated: imported from vendor advisories with machine assistance, not yet individually verified. Confirm against your vendor's advisory before acting, and report anything wrong.