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2187582c36
We use high_memory as a measure for amount of memory available in determining the required minimum size of our IOVA space with the assumption that one rarely maps more than the available memory for DMA. In special cases like mapping significant amounts of memory more than once this can still be tuned with the s390_iommu_apterture kernel parameter. In this use case high_memory is treated as a physical address. As high_memory is a virtual address however this means we need to convert it using virt_to_phys() before use Note that at the moment physical and virtual addresses are identical so this mismatch does not currently cause trouble. Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@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 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.