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It is possible, under obscure circumstances, to convince the ITS driver to emit a SYNC operation that targets a collection that is not bound to any redistributor (and the target_address field is zero) because the corresponding CPU has not been seen yet (the system has been booted with max_cpus="something small"). If the ITS is using the linear CPU number as the target, this is not a big deal, as we just end-up issuing a SYNC to CPU0. But if the ITS requires the physical address of the redistributor (with GITS_TYPER.PTA==1), we end-up asking the ITS to write to the physical address zero, which is not exactly a good idea (there has been report of the ITS locking up). This should of course never happen, but hey, this is SW... In order to avoid the above disaster, let's track which collections have been actually initialized, and let's not generate a SYNC if the collection hasn't been properly bound to a redistributor. Take this opportunity to spit our a warning, in the hope that someone may report the issue if it arrises again. Reported-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Jason Cooper <jason@lakedaemon.net> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com> Cc: Sumit Garg <sumit.garg@linaro.org> Link: https://lkml.kernel.org/r/20180622095254.5906-6-marc.zyngier@arm.com |
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| README | ||
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.
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.