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e2cf43d595
The XIVE driver deals with CPU IPIs in a peculiar way. Each CPU has its own XIVE IPI interrupt allocated at the HW level, for PowerNV, or at the hypervisor level for pSeries. In practice, these interrupts are not always used. pSeries/PowerVM prefers local doorbells for local threads since they are faster. On PowerNV, global doorbells are also preferred for the same reason. The mapping in the Linux is reduced to a single interrupt using HW interrupt number 0 and a custom irq_chip to handle EOI. This can cause performance issues in some benchmark (ipistorm) on multichip systems. Clarify the use of the 0 value, it will help in improving multichip support. Signed-off-by: Cédric Le Goater <clg@kaod.org> Reviewed-by: Greg Kurz <groug@kaod.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201210171450.1933725-4-clg@kaod.org
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.