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authorFenghua Yu <fenghua.yu@intel.com>2009-06-19 16:47:29 -0400
committerDavid Woodhouse <David.Woodhouse@intel.com>2009-06-23 17:07:54 -0400
commit2c2e2c389d03bb16b8cdf9db3ac615385fac100f (patch)
tree19af024e80adbbd1536aae0fa0c23ed4249834fe /arch
parent687d680985b1438360a9ba470ece8b57cd205c3b (diff)
IOMMU Identity Mapping Support (drivers/pci/intel_iommu.c)
Identity mapping for IOMMU defines a single domain to 1:1 map all PCI devices to all usable memory. This reduces map/unmap overhead in DMA API's and improve IOMMU performance. On 10Gb network cards, Netperf shows no performance degradation compared to non-IOMMU performance. This method may lose some of DMA remapping benefits like isolation. The patch sets up identity mapping for all PCI devices to all usable memory. In the DMA API, there is no overhead to maintain page tables, invalidate iotlb, flush cache etc. 32 bit DMA devices don't use identity mapping domain, in order to access memory beyond 4GiB. When kernel option iommu=pt, pass through is first tried. If pass through succeeds, IOMMU goes to pass through. If pass through is not supported in hw or fail for whatever reason, IOMMU goes to identity mapping. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'arch')
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