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b03cbca48d
Support identity domains for devices that do not offer the VIRTIO_IOMMU_F_BYPASS_CONFIG feature, by creating 1:1 mappings between the virtual and physical address space. Identity domains created this way still perform noticeably better than DMA domains, because they don't have the overhead of setting up and tearing down mappings at runtime. The performance difference between this and bypass is minimal in comparison. It does not matter that the physical addresses in the identity mappings do not all correspond to memory. By enabling passthrough we are trusting the device driver and the device itself to only perform DMA to suitable locations. In some cases it may even be desirable to perform DMA to MMIO regions. Reviewed-by: Eric Auger <eric.auger@redhat.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Link: https://lore.kernel.org/r/20211201173323.1045819-6-jean-philippe@linaro.org Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.