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@intel.com wrote:
From: Ira Weiny ira.weiny@intel.com
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
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?
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