2014-06-26 22:05 GMT+08:00 Paolo Bonzini <pbonz...@redhat.com>: > Il 26/06/2014 16:01, Le Tan ha scritto: > >> Hi Paolo, >> I am adding intel-iommu emulation to q35 for the GSoC project. I am >> confused about AddressSpace and I believe that you can help me. :) >> 1. For intel-iommu emulation, I have to read the translation >> structures from guest memory, that is, the guest will prepare some >> tables in memory and write the physical address of them to a register >> of intel-iommu, and I need to access those structures. I use >> dma_memory_read(&address_space_memory,...) to do this. Is that right? >> I am not sure that whether accesses to address_space_memory will be >> translated through IOMMU. I think the answer is not, because I see >> that cpu_physical_memory_read() also use address_space_memory as >> AddressSpace. > > > Correct. > > >> 2. In my opinion, I have to init a AddressSpace and link it with my >> IOMMU MemoryRegion, then the bus uses this AddressSpace to translate >> the accesses. Is that right? For q35, how can I register my IOMMU >> MemoryRegion to the bus? I see that there is function >> pci_setup_iommu() that links a AddressSpace to the bus to translate >> accesses to PCI into system memory. Is that related? I think q35 >> should maintain a bus AddressSpace, but I can't find it. >> What do you think? > > > Right now, the q35 PCI host does not define an iommu_fn, so the default DMA > address space is used by pci_device_iommu_address_space. This is just > address_space_memory. > > The iommu_fn is set with pci_setup_iommu. Commit ae74bbe (apb: implement > IOMMU translation for PCI host bridge, 2014-05-28) provides an example of > how to prepare an IOMMU memory region, add it to an address space, and > return that address space from an iommu_fn.
Hi Paolo, I have added the address space to q35 and the translate function of intel_iommu is called. :) However, I still have some questions here. 1. In struct IOMMUTLBEntry, I think the addr_mask field should be the mask of the page offset, right? But I see different usages of this field. In spapr_tce_translate_iommu(), the addr_mask field is assigned with the mask of the page offset. However, in pbm_translate_iommu(), in the passthrough case, the addr_mask field seems to be assigned the mask of the page number. Is there any problem here? 2. For q35, how to identify origination of DMA requests? The VT-d manual says we should use source-id(for PCI-Express devices, it is requester identifier) to map devices to domains. What is the related part in QEMU? Where can I get the source-id of a DMA request? Thanks very much! Le > Thanks, > > Paolo > > >> Thanks very much! >> >> Regards, >> Le Tan >> >
