diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2021-11-19 16:43:55 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-11-20 10:35:54 -0800 |
| commit | 825c43f50e3aa811a291ffcb40e02fbf6d91ba86 (patch) | |
| tree | 729daf64405cf0fe6c772150b5ec0eb283c0fb8c /mm/Kconfig | |
| parent | d78f3853f831eee46c6dbe726debf3be9e9c0d05 (diff) | |
kmap_local: don't assume kmap PTEs are linear arrays in memory
The kmap_local conversion broke the ARM architecture, because the new
code assumes that all PTEs used for creating kmaps form a linear array
in memory, and uses array indexing to look up the kmap PTE belonging to
a certain kmap index.
On ARM, this cannot work, not only because the PTE pages may be
non-adjacent in memory, but also because ARM/!LPAE interleaves hardware
entries and extended entries (carrying software-only bits) in a way that
is not compatible with array indexing.
Fortunately, this only seems to affect configurations with more than 8
CPUs, due to the way the per-CPU kmap slots are organized in memory.
Work around this by permitting an architecture to set a Kconfig symbol
that signifies that the kmap PTEs do not form a lineary array in memory,
and so the only way to locate the appropriate one is to walk the page
tables.
Link: https://lore.kernel.org/linux-arm-kernel/20211026131249.3731275-1-ardb@kernel.org/
Link: https://lkml.kernel.org/r/20211116094737.7391-1-ardb@kernel.org
Fixes: 2a15ba82fa6c ("ARM: highmem: Switch to generic kmap atomic")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reported-by: Quanyang Wang <quanyang.wang@windriver.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/Kconfig')
| -rw-r--r-- | mm/Kconfig | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index 068ce591a13a..28edafc820ad 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -890,6 +890,9 @@ config MAPPING_DIRTY_HELPERS config KMAP_LOCAL bool +config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY + bool + # struct io_mapping based helper. Selected by drivers that need them config IO_MAPPING bool |