AMD SEV firmware - missing checks around RMP initialization (AMD-SB-3023): MULTI-TENANT ISOLATION: Missing checks

Impact

MULTI-TENANT ISOLATION: Missing checks around RMP initialization lead to I/O memory being misidentified, weakening the boundary the reverse-map table enforces. Lowest-severity member of the AMD-SB-3023 RMP batch; include it in the same firmware pass rather than tracking it separately.

Who can reach it

Local, privileged, during SNP platform initialization.

What to do

Fixed in AMD PI/AGESA firmware and delivered only as an OEM SBIOS package - AMD ships the PI drop to Dell, HPE, Supermicro, Lenovo and the ODMs, who each requalify before releasing BIOS. **Budget one to six months of OEM lag**, and note that several CVEs in this batch are marked 'no fix planned' on Naples (EPYC 7001) - for those the only remediation is retiring the hardware. Applying it means cordon, drain and a full power cycle per node; there is no driver reload, no live patch and no VBIOS step. Because this touches the SEV-SNP trust boundary, the update moves the platform TCB version: refresh VCEK certificates from AMD's KDS and update tenant attestation policy, or confidential guest launches will fail immediately after the BIOS lands.

References