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The RMPREAD instruction returns an architecture defined format of an RMP entry. This is the preferred method for examining RMP entries. In preparation for using the RMPREAD instruction, convert the existing code that directly accesses the RMP to map the raw RMP information into the architecture defined format. RMPREAD output returns a status bit for the 2MB region status. If the input page address is 2MB aligned and any other pages within the 2MB region are assigned, then 2MB region status will be set to 1. Otherwise, the 2MB region status will be set to 0. For systems that do not support RMPREAD, calculating this value would require looping over all of the RMP table entries within that range until one is found with the assigned bit set. Since this bit is not defined in the current format, and so not used today, do not incur the overhead associated with calculating it. Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Nikunj A Dadhania <nikunj@amd.com> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Link: https://lore.kernel.org/r/da49d5af1eb7f9039f35f14a32ca091efb2dd818.1733172653.git.thomas.lendacky@amd.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.