Messages in this thread |  | | | Date | Thu, 18 Jun 2009 21:25:45 +0300 | | From | Muli Ben-Yehuda <> | | Subject | Re: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition |
On Thu, Jun 18, 2009 at 11:14:51AM -0700, Yu, Fenghua wrote: > > > >On Thu, Jun 18, 2009 at 11:05:14AM -0700, Fenghua Yu wrote: > > > >> IOMMU Identity Mapping Support: iommu_identity_mapping definition > >> > >> Identity mapping for IOMMU defines a single domain to 1:1 map all > >> pci devices to all usable memory. > > > >Why use VT-d at all in this case? Do you have a use-case in mind? > > Some users want to use VT-d in KVM but are concerned of DMA > remapping performance. They can use identity mapping and still have > KVM on VT-d. They can also use pass through patch (sent out before) > if hardware supports pass through.
Sorry, I must be missing something. For the normal device assignment case, we want the IOMMU page tables to have gpa->hpa mappings rather than the 1-1 identity mapping. How do you envision the 1-1 mapping being used in the device assignment case?
Cheers, Muli -- Muli Ben-Yehuda | muli@il.ibm.com | +972-4-8281080 Manager, Virtualization and Systems Architecture Master Inventor, IBM Haifa Research Laboratory
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