b8fcd0e588
The ACPICA's strategy with respect to the handling of memory mappings associated with memory operation regions is to avoid mapping the entire region at once which may be problematic at least in principle (for example, it may lead to conflicts with overlapping mappings having different attributes created by drivers). It may also be wasteful, because memory opregions on some systems take up vast chunks of address space while the fields in those regions actually accessed by AML are sparsely distributed. For this reason, a one-page "window" is mapped for a given opregion on the first memory access through it and if that "window" does not cover an address range accessed through that opregion subsequently, it is unmapped and a new "window" is mapped to replace it. Next, if the new "window" is not sufficient to acess memory through the opregion in question in the future, it will be replaced with yet another "window" and so on. That may lead to a suboptimal sequence of memory mapping and unmapping operations, for example if two fields in one opregion separated from each other by a sufficiently wide chunk of unused address space are accessed in an alternating pattern. The situation may still be suboptimal if the deferred unmapping introduced previously is supported by the OS layer. For instance, the alternating memory access pattern mentioned above may produce a relatively long list of mappings to release with substantial duplication among the entries in it, which could be avoided if acpi_ex_system_memory_space_handler() did not release the mapping used by it previously as soon as the current access was not covered by it. In order to improve that, modify acpi_ex_system_memory_space_handler() to preserve all of the memory mappings created by it until the memory regions associated with them go away. Accordingly, update acpi_ev_system_memory_region_setup() to unmap all memory associated with memory opregions that go away. Reported-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Xiang Li <xiang.z.li@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.