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The APIC, per spec, is fundamentally confused and thinks that interrupt vectors 16-31 are valid. This makes no sense -- the CPU reserves vectors 0-31 for exceptions (faults, traps, etc). Obviously, no device should actually produce an interrupt with vector 16-31, but robustness can be improved by setting the APIC TPR class to 1, which will prevent delivery of an interrupt with a vector below 32. Note: This is *not* intended as a security measure against attackers who control malicious hardware. Any PCI or similar hardware that can be controlled by an attacker MUST be behind a functional IOMMU that remaps interrupts. The purpose of this change is to reduce the chance that a certain class of device malfunctions crashes the kernel in hard-to-debug ways. Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/dc04a9f8b234d7b0956a8d2560b8945bcd9c4bf7.1563117760.git.luto@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.