090bad39b2
We want to support sparse memory and therefore huge chunks of DMA windows do not need to be mapped. If a DMA window big enough to require 2 or more indirect levels, and a DMA window is used to map all RAM (which is a default case for 64bit window), we can actually save some memory by not allocation TCE for regions which we are not going to map anyway. The hardware tables alreary support indirect levels but we also keep host-physical-to-userspace translation array which is allocated by vmalloc() and is a flat array which might use quite some memory. This converts it_userspace from vmalloc'ed array to a multi level table. As the format becomes platform dependend, this replaces the direct access to it_usespace with a iommu_table_ops::useraddrptr hook which returns a pointer to the userspace copy of a TCE; future extension will return NULL if the level was not allocated. This should not change non-KVM handling of TCE tables and it_userspace will not be allocated for non-KVM tables. Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.