On Mon, 3 Oct 2022 at 20:52, Ira Weiny <ira.weiny@xxxxxxxxx> wrote: > > On Mon, Oct 03, 2022 at 02:55:02PM +0530, Sumit Garg wrote: > > Hi Ira, > > > > On Sun, 2 Oct 2022 at 05:53, <ira.weiny@xxxxxxxxx> wrote: > > > > > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > > > > > get_kernel_pages() only had one caller [shm_get_kernel_pages()] which did not > > > need the functionality it provided. Furthermore, it called kmap_to_page() > > > which we are looking to removed. > > > > > > Alter shm_get_kernel_pages() to no longer call get_kernel_pages() and remove > > > get_kernel_pages(). Along the way it was noted that shm_get_kernel_pages() > > > does not have any need to support vmalloc'ed addresses either. Remove that > > > functionality to clean up the logic. > > > > > > This series also fixes and uses is_kmap_addr(). > > > > From the above description, I am failing to see the motivation behind > > this change. Can you elaborate here? > > Al Viro found[1] that kmap_to_page() is broken. But not only was it broken but > it presents confusion over how highmem should be used because kmap() and > friends should not be used for 'long term' mappings. > > [1] https://lore.kernel.org/lkml/YzSSl1ItVlARDvG3@ZenIV > Thanks for the background info. This should be part of the cover letter. > > > > Also, since you are targeting to remove kmap_to_page(), is there any > > alternative way to support highmem for future TEE bus drivers? As I > > can see higmem being enabled for multiple Arm defconfigs [1] which can > > also support TEE (an example which already does it: > > arch/arm/configs/imx_v6_v7_defconfig). > > With TEE how are the highmem pages used? Right now the code does not seem to > use any user pages. So I can't really say how this should work. Why does the > kernel need a mapping of those pages? Fair enough, I don't have a real kernel driver use-case for highmem which is required to be registered with TEE. -Sumit > > Ira > > > > > [1] git grep CONFIG_HIGHMEM arch/arm/ > > > > -Sumit > > > > > > > > Ira Weiny (4): > > > highmem: Enhance is_kmap_addr() to check kmap_local_page() mappings > > > tee: Remove vmalloc page support > > > tee: Remove call to get_kernel_pages() > > > mm: Remove get_kernel_pages() > > > > > > drivers/tee/tee_shm.c | 41 ++++++++++++-------------------- > > > include/linux/highmem-internal.h | 5 +++- > > > include/linux/mm.h | 2 -- > > > mm/swap.c | 30 ----------------------- > > > 4 files changed, 19 insertions(+), 59 deletions(-) > > > > > > > > > base-commit: 274d7803837da78dfc911bcda0d593412676fc20 > > > -- > > > 2.37.2 > > >
