[PATCH 1/1] riscv: Implement arch_sync_kernel_mappings() for "preventive" TLB flush

[kernel test robot]

Hi Dylan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.5-rc5 next-20230807]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dylan-Jhong/riscv-Implement-arch_sync_kernel_mappings-for-preventive-TLB-flush/20230807-162922
base:   linus/master
patch link:    https://lore.kernel.org/r/20230807082305.198784-2-dylan%40andestech.com
patch subject: [PATCH 1/1] riscv: Implement arch_sync_kernel_mappings() for "preventive" TLB flush
config: riscv-allyesconfig (https://download.01.org/0day-ci/archive/20230807/202308071710.irjERWVF-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 12.3.0
reproduce: (https://download.01.org/0day-ci/archive/20230807/202308071710.irjERWVF-lkp@intel.com/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 at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308071710.irjERWVF-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/riscv/mm/tlbflush.c:159:6: warning: no previous prototype for 'arch_sync_kernel_mappings' [-Wmissing-prototypes]
     159 | void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/arch_sync_kernel_mappings +159 arch/riscv/mm/tlbflush.c

   152	
   153	/*
   154	 * Since RISC-V is a microarchitecture that allows caching invalid entries in the TLB,
   155	 * it is necessary to issue a "preventive" SFENCE.VMA to ensure that each core obtains
   156	 * the correct kernel mapping. arch_sync_kernel_mappings() will ensure that kernel
   157	 * page table mappings created via vmap/vmalloc() are updated before switching MM.
   158	 */
 > 159	void arch_sync_kernel_mappings(unsigned long start, unsigned long end)

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