On giovedì 30 giugno 2022 17:17:24 CEST Alexander Duyck wrote: > On Thu, Jun 30, 2022 at 3:10 AM Maciej Fijalkowski > <maciej.fijalkowski@xxxxxxxxx> wrote: > > > > On Wed, Jun 29, 2022 at 10:58:36AM +0200, Fabio M. De Francesco wrote: > > > The use of kmap() is being deprecated in favor of kmap_local_page(). > > > > > > With kmap_local_page(), the mapping is per thread, CPU local and not > > > globally visible. Furthermore, the mapping can be acquired from any context > > > (including interrupts). > > > > > > Therefore, use kmap_local_page() in ixgbe_check_lbtest_frame() because > > > this mapping is per thread, CPU local, and not globally visible. > > > > Hi, > > > > I'd like to ask why kmap was there in the first place and not plain > > page_address() ? > > > > Alex? > > The page_address function only works on architectures that have access > to all of physical memory via virtual memory addresses. The kmap > function is meant to take care of highmem which will need to be mapped > before it can be accessed. > > For non-highmem pages kmap just calls the page_address function. > https://elixir.bootlin.com/linux/latest/source/include/linux/highmem-internal.h#L40 Please take a look at documentation (highmem.rst). I've recently reworked it and added information about kmap_local_page() Thanks, Fabio > > Thanks, > > - Alex >
