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Add the Dat-Enhancement facility 1 to the list of facilities which are required to start the kernel. The facility provides the CSPG and IDTE instructions. In particular the CSPG instruction can be used to replace a valid page table entry with a different page table entry, which also differs in the page frame real address. Without the CSPG instruction it is possible to use the CSP instruction to change valid page table entries, however it only allows to change the lower or higher 32 bits of such entries, which means it cannot be used to change the page frame real address of valid page table entries. Given that there is code around (e.g. HugeTLB vmemmap optimization) which requires to change valid page table entries of the kernel mapping, without the detour over an invalid page table entry, make the CSPG instruction unconditionally available. The Dat-Enhancement facility 1 is available since z990, which is older than the currently supported minimum architecture (z10). Therefore adding this to the architecture level set shouldn't cause any problems. Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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 reStructuredText 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.