[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Full virtualization and I/O
Mats, > For fully virtualized mode (hardware supported virtual machine, such as > Finally, while I'm on the subject of fully virtualized mode: It is > currently not possible to give a DMA-based device to a fully-virtualized > domain. The reason for this is that the guest OS will have been told > that memory is from 0..256MB (say), and it's actual machine physical > address is at 256MB..512MB. The OS is completely unaware of this > "mismatch". So the OS will perform some operation to take a virtual > address of some buffer (say a network packet) and make it into a > "physical address", which will be an address in the range of 0..256MB. > This will of course (at least) lead to the wrong data being transmitted, > as the address of the actual data is somewhere in the range > 256MB..512MB. The only solution to this is to have an IOMMU, which can > translate the guest's understanding of a physical address (0..256MB) to > a machine physical address (256..512MB). I know that individual domains can be given direct access to individual PCI devices. http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user/user.html#SE CTION03230000000000000000 Is this not possible with HVM domains? Is it possible for HVM domains to be a PCI frontend and receive a PCI device which is "hidden" from Dom0? Or is this what paravirtualized drivers for HVM domains are doing? Thanks, Aravindh _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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