3c0468d445
Currently both iommu_alloc_coherent() and iommu_free_coherent() align the desired allocation size to PAGE_SIZE, and gets system pages and IOMMU mappings (TCEs) for that value. When IOMMU_PAGE_SIZE < PAGE_SIZE, this behavior may cause unnecessary TCEs to be created for mapping the whole system page. Example: - PAGE_SIZE = 64k, IOMMU_PAGE_SIZE() = 4k - iommu_alloc_coherent() is called for 128 bytes - 1 system page (64k) is allocated - 16 IOMMU pages (16 x 4k) are allocated (16 TCEs used) It would be enough to use a single TCE for this, so 15 TCEs are wasted in the process. Update iommu_*_coherent() to make sure the size alignment happens only for IOMMU_PAGE_SIZE() before calling iommu_alloc() and iommu_free(). Also, on iommu_range_alloc(), replace ALIGN(n, 1 << tbl->it_page_shift) with IOMMU_PAGE_ALIGN(n, tbl), which is easier to read and does the same. Signed-off-by: Leonardo Bras <leobras.c@gmail.com> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210318174414.684630-1-leobras.c@gmail.com |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.