2de8b4cc20
Originally, I was convinced that we needed to use tmpalias flushes everwhere, for both user and kernel flushes. However, when I modified flush_kernel_dcache_page_addr, to use a tmpalias flush, my c8000 would crash quite early when booting. The PDC returns alias values of 0 for the icache and dcache. This indicates that either the alias boundary is greater than 16MB or equivalent aliasing doesn't work. I modified the tmpalias code to make it easy to try alternate boundaries. I tried boundaries up to 128MB but still kernel tmpalias flushes didn't work on c8000. This led me to conclude that tmpalias flushes don't work on PA8800 and PA8900 machines, and that we needed to flush directly using the virtual address of user and kernel pages. This is likely the major cause of instability on the c8000 and rp34xx machines. Flushing user pages requires doing a temporary context switch as we have to flush pages that don't belong to the current context. Further, we have to deal with pages that aren't present. If a page isn't present, the flush instructions fault on every line. Other code has been rearranged and simplified based on testing. For example, I introduced a flush_cache_dup_mm routine. flush_cache_mm and flush_cache_dup_mm differ in that flush_cache_mm calls purge_cache_pages and flush_cache_dup_mm calls flush_cache_pages. In some implementations, pdc is more efficient than fdc. Based on my testing, I don't believe there's any performance benefit on the c8000. Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de>
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.