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When struct its_device instances are created, the nr_ites member will be set to a power of 2 that equals or exceeds the requested number of MSIs passed to the msi_prepare() callback. At the same time, the LPI map is allocated to be some multiple of 32 in size, where the allocated size may be less than the requested size depending on whether a contiguous range of sufficient size is available in the global LPI bitmap. This may result in the situation where the nr_ites < nr_lpis, and since nr_ites is what we program into the hardware when we map the device, the additional LPIs will be non-functional. For bog standard hardware, this does not really matter. However, in cases where ITS device IDs are shared between different PCIe devices, we may end up allocating these additional LPIs without taking into account that they don't actually work. So let's make nr_ites at least 32. This ensures that all allocated LPIs are 'live', and that its_alloc_device_irq() will fail when attempts are made to allocate MSIs beyond what was allocated in the first place. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [maz: updated comment] Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
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.