include/linux/bitops.h:273:19: sparse: sparse: cast truncates bits from constant value (fffffffffff000 becomes fffff000)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   94515f3a7d4256a5062176b7d6ed0471938cd51a
commit: e71e00127110dedc6a9e746178282b4dac97ed96 iommupt: Add the RISC-V page table format
date:   4 months ago
config: um-randconfig-r121-20260716 (https://download.01.org/0day-ci/archive/20260718/[email protected]/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260718/[email protected]/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
| Fixes: e71e00127110 ("iommupt: Add the RISC-V page table format")
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

sparse warnings: (new ones prefixed by >>)
   drivers/iommu/generic_pt/fmt/iommu_riscv64.c: note: in included file (through drivers/iommu/generic_pt/fmt/../pt_log2.h, drivers/iommu/generic_pt/fmt/../pt_defs.h, drivers/iommu/generic_pt/fmt/iommu_template.h):
>> include/linux/bitops.h:273:19: sparse: sparse: cast truncates bits from constant value (fffffffffff000 becomes fffff000)
   include/linux/bitops.h:278:16: sparse: sparse: cast truncates bits from constant value (fffffffffff000 becomes fffff000)
>> include/linux/bitops.h:273:19: sparse: sparse: cast truncates bits from constant value (fffffffffff000 becomes fffff000)
   include/linux/bitops.h:278:16: sparse: sparse: cast truncates bits from constant value (fffffffffff000 becomes fffff000)

vim +273 include/linux/bitops.h

c320592f3f2a1e Wolfram Sang       2025-01-07  261  
952043ac12a117 Steven Whitehouse  2009-04-23  262  /**
952043ac12a117 Steven Whitehouse  2009-04-23  263   * __ffs64 - find first set bit in a 64 bit word
952043ac12a117 Steven Whitehouse  2009-04-23  264   * @word: The 64 bit word
952043ac12a117 Steven Whitehouse  2009-04-23  265   *
4945cca232ce8b Geert Uytterhoeven 2021-02-25  266   * On 64 bit arches this is a synonym for __ffs
952043ac12a117 Steven Whitehouse  2009-04-23  267   * The result is not defined if no bits are set, so check that @word
952043ac12a117 Steven Whitehouse  2009-04-23  268   * is non-zero before calling this.
952043ac12a117 Steven Whitehouse  2009-04-23  269   */
6606c8c7e81886 Kees Cook          2025-08-04  270  static inline __attribute_const__ unsigned int __ffs64(u64 word)
952043ac12a117 Steven Whitehouse  2009-04-23  271  {
952043ac12a117 Steven Whitehouse  2009-04-23  272  #if BITS_PER_LONG == 32
952043ac12a117 Steven Whitehouse  2009-04-23 @273  	if (((u32)word) == 0UL)
952043ac12a117 Steven Whitehouse  2009-04-23  274  		return __ffs((u32)(word >> 32)) + 32;
952043ac12a117 Steven Whitehouse  2009-04-23  275  #elif BITS_PER_LONG != 64
952043ac12a117 Steven Whitehouse  2009-04-23  276  #error BITS_PER_LONG not 32 or 64
952043ac12a117 Steven Whitehouse  2009-04-23  277  #endif
952043ac12a117 Steven Whitehouse  2009-04-23  278  	return __ffs((unsigned long)word);
952043ac12a117 Steven Whitehouse  2009-04-23  279  }
952043ac12a117 Steven Whitehouse  2009-04-23  280  

:::::: The code at line 273 was first introduced by commit
:::::: 952043ac12a117d8e94bddd9088338d7ad20ca7d bitops: Add __ffs64 bitop

:::::: TO: Steven Whitehouse <[email protected]>
:::::: CC: Steven Whitehouse <[email protected]>

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki