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The IODA2 specification says that a 64 DMA address cannot use top 4 bits (3 are reserved and one is a "TVE select"); bottom page_shift bits cannot be used for multilevel table addressing either. The existing IODA2 table allocation code aligns the minimum TCE table size to PAGE_SIZE so in the case of 64K system pages and 4K IOMMU pages, we have 64-4-12=48 bits. Since 64K page stores 8192 TCEs, i.e. needs 13 bits, the maximum number of levels is 48/13 = 3 so we physically cannot address more and EEH happens on DMA accesses. This adds a check that too many levels were requested. It is still possible to have 5 levels in the case of 4K system page size. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Acked-by: Gavin Shan <gwshan@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.