An IOMMU group represents the smallest set of devices that are considered to be isolated. All devices belonging to an IOMMU group share a default domain for DMA APIs. There are two types of default domain: IOMMU_DOMAIN_DMA and IOMMU_DOMAIN_IDENTITY. The former means IOMMU translation, while the latter means IOMMU by-pass.
Currently, the default domain type for the IOMMU groups is determined globally. All IOMMU groups use a single default domain type. The global default domain type can be adjusted by kernel build configuration or kernel parameters. More and more users are looking forward to a fine grained default domain type. For example, with the global default domain type set to translation, the OEM verndors or end users might want some trusted and fast-speed devices to bypass IOMMU for performance gains. On the other hand, with global default domain type set to by-pass, some devices with limited system memory addressing capability might want IOMMU translation to remove the bounce buffer overhead. This series proposes per-group default domain type to meet these demands. It adds a per-device iommu_passthrough attribute. By setting this attribute, end users or device vendors are able to tell the IOMMU subsystem that this device is willing to use a default domain of IOMMU_DOMAIN_IDENTITY. The IOMMU device probe procedure is reformed to pre-allocate groups for all devices on a specific bus before adding the devices into the groups. This enables the IOMMU device probe precedure to determine a per-group default domain type before allocating IOMMU domains and attaching them to devices. Please help to review it. Your comments and suggestions are appricated. Best regards, baolu Lu Baolu (4): driver core: Add iommu_passthrough to struct device PCI: Add "pci=iommu_passthrough=" parameter for iommu passthrough iommu: Preallocate iommu group when probing devices iommu: Determine default domain type before allocating domain .../admin-guide/kernel-parameters.txt | 5 + drivers/iommu/iommu.c | 127 ++++++++++++++---- drivers/pci/pci.c | 34 +++++ drivers/pci/pci.h | 1 + drivers/pci/probe.c | 2 + include/linux/device.h | 3 + 6 files changed, 143 insertions(+), 29 deletions(-) -- 2.17.1 _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
