Xen on older AMD CPUs - 64-bit PV guest processor erratum: Xen 4.0 and 4.1 running a 64-bit PV guest on older AMD CPUs

Impact

Xen 4.0 and 4.1 running a 64-bit PV guest on older AMD CPUs did not protect against a processor erratum, letting a guest OS user hang the host. Historical, but it is the earliest entry in a long pattern worth naming: AMD CPU errata that a hypervisor must actively work around, where forgetting the workaround hands guests a host-availability lever.

Who can reach it

From inside a 64-bit PV guest on affected legacy AMD silicon.

What to do

Fixed in Xen (XSA-9). Hypervisor update plus reboot. Affected silicon is long retired; carried here for completeness of the AMD virtualisation history rather than as an action item.

References

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