I'm trying to understand the purpose of the permissive flag in the Xen pciback driver. The comments in the code suggest that setting permissive=1 is "potentially unsafe", and I've been wondering why? My thinking goes this way -- we either: 1) have IOMMU/VT-d in the system, and use it to isolate the device assigned to a DomU, in which case allowing the DomU to fully control the assigned device's config space should not be a problem because VT-d should do its job (we hope at least ;), or 2) we don't have IOMMU/VT-d, in which case assigning a device to anything other than Dom0 is simply insecure, no matter if we try to restrict access to config space (but still allow DMA engine to be programmed by DomU) or not. So, what am I missing here? joanna.
Description: OpenPGP digital signature
_______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel