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the maximum number of VT-d domains (256 on a Sandybridge). We now allocate a VT-d domain for a guest only if the administrator has explicitly configured one or more PCI passthru device(s). If there are no PCI passthru devices configured (the common case) then the number of virtual machines is no longer limited by the maximum number of VT-d domains. Reviewed by: grehan@ Approved by: re@