RE: [PATCH 1/2] IOMMU Identity Mapping Support:iommu_identity_mapping definition

From: Yu, Fenghua
Date: Thu Jun 18 2009 - 14:15:03 EST

>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


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at