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Versions Affected : All versions prior to TrueNAS 12.0-U8


A Hyper-V vPCI emulation change can cause SR-IOV (Single-Root I/O Virtualization) and DDA (Discrete Device Assignment) devices to fail to operate correctly under Hyper-V.

In recent Hyper-V releases on Windows Server 2022, the vPCI code does not initialize the last 4 bit of device registers. This behavior change could result in failure to initialize guest drivers for SR-IOV or DDA devices. SR-IOV and DDA devices may not work in FreeBSD running under certain Hyper-V releases.


No workaround is available, however systems not running within Hyper-V or Azure are unaffected.


  • Upgrade to TrueNAS 12.0-U8 or later.


Further information