6a036afb55
Neoverse-N1 cores with the 'COHERENT_ICACHE' feature may fetch stale instructions when software depends on prefetch-speculation-protection instead of explicit synchronization. [0] The workaround is to trap I-Cache maintenance and issue an inner-shareable TLBI. The affected cores have a Coherent I-Cache, so the I-Cache maintenance isn't necessary. The core tells user-space it can skip it with CTR_EL0.DIC. We also have to trap this register to hide the bit forcing DIC-aware user-space to perform the maintenance. To avoid trapping all cache-maintenance, this workaround depends on a firmware component that only traps I-cache maintenance from EL0 and performs the workaround. For user-space, the kernel's work is to trap CTR_EL0 to hide DIC, and produce a fake IminLine. EL3 traps the now-necessary I-Cache maintenance and performs the inner-shareable-TLBI that makes everything better. [0] https://developer.arm.com/docs/sden885747/latest/arm-neoverse-n1-mp050-software-developer-errata-notice * for-next/neoverse-n1-stale-instr: arm64: Silence clang warning on mismatched value/register sizes arm64: compat: Workaround Neoverse-N1 #1542419 for compat user-space arm64: Fake the IminLine size on systems affected by Neoverse-N1 #1542419 arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419
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.