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In the opencapi protocol, host memory contexts are referenced by a 'actag'. During setup, a driver must tell the device how many actags it can used, and what values are acceptable. On POWER9, the NPU can handle 64 actags per link, so they must be shared between all the PCI functions of the link. To get a global picture of how many actags are used by each AFU of every function, we capture some data at the end of PCI enumeration, so that actags can be shared fairly if needed. This is not powernv specific per say, but rather a consequence of the opencapi configuration specification being quite general. The number of available actags on POWER9 makes it more likely to be hit. This is somewhat mitigated by the fact that existing AFUs are coded by requesting a reasonable count of actags and existing devices carry only one AFU. Signed-off-by: Frederic Barrat <fbarrat@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.