Messages in this thread | | | From | "Yu, Fenghua" <> | Date | Thu, 18 Jun 2009 11:14:51 -0700 | Subject | RE: [PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition |
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> >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.
By default, identity mapping is turned off. "iommu=identity" can turn it on
Thanks.
-Fenghua
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