On 16/10/2024 23:05, Jann Horn wrote:
On Wed, Oct 16, 2024 at 8:05 PM kernel test robot <lkp@xxxxxxxxx> wrote:
[auto build test ERROR on 6485cf5ea253d40d507cd71253c9568c5470cd27]
url: https://github.com/intel-lab-lkp/linux/commits/Jann-Horn/comedi-Flush-partial-mappings-in-error-case/20241016-022809
base: 6485cf5ea253d40d507cd71253c9568c5470cd27
patch link: https://lore.kernel.org/r/20241015-comedi-tlb-v2-1-cafb0e27dd9a%40google.com
patch subject: [PATCH v2] comedi: Flush partial mappings in error case
config: arm-randconfig-004-20241016 (https://download.01.org/0day-ci/archive/20241017/202410170111.K30oyTWa-lkp@xxxxxxxxx/config)
compiler: arm-linux-gnueabi-gcc (GCC) 14.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241017/202410170111.K30oyTWa-lkp@xxxxxxxxx/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410170111.K30oyTWa-lkp@xxxxxxxxx/
All errors (new ones prefixed by >>):
arm-linux-gnueabi-ld: drivers/comedi/comedi_fops.o: in function `comedi_mmap':
comedi_fops.c:(.text+0x4be): undefined reference to `zap_vma_ptes'
Ugh, this one is from a nommu build ("# CONFIG_MMU is not set"), it
makes sense that you can't zap PTEs when you don't have any PTEs at
all... what really impresses me about this is that the rest of the
code compiles on nommu. I'm pretty sure this codepath wouldn't
actually _work_ on nommu, but apparently compiling it works?
I don't know what the right fix is here - should the entire comedi
driver be gated on CONFIG_MMU, or only a subset of the mmap handler,
or something else?
Given that it would also affect a lot of fbdev drivers that would also
benefit from zapping partial mappings, I suggest that gating on
CONFIG_MMU would not be the correct fix.
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