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To implement the get/set_irqchip_state callbacks (limited to the PENDING state), we have to use a particular set of hacks: - Reading the pending state is done by using a pair of new redistributor registers (GICR_VSGIR, GICR_VSGIPENDR), which allow the 16 interrupts state to be retrieved. - Setting the pending state is done by generating it as we'd otherwise do for a guest (writing to GITS_SGIR). - Clearing the pending state is done by emitting a VSGI command with the "clear" bit set. This requires some interesting locking though: - When talking to the redistributor, we must make sure that the VPE affinity doesn't change, hence taking the VPE lock. - At the same time, we must ensure that nobody accesses the same redistributor's GICR_VSGIR registers for a different VPE, which would corrupt the reading of the pending bits. We thus take the per-RD spinlock. Much fun. Signed-off-by: Marc Zyngier <maz@kernel.org> Reviewed-by: Zenghui Yu <yuzenghui@huawei.com> Link: https://lore.kernel.org/r/20200304203330.4967-12-maz@kernel.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.