include/linux/bitops.h:273:19: sparse: sparse: cast truncates bits from constant value (ffffffffff000 becomes fffff000)

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   e1914add2799225a87502051415fc5c32aeb02ae
commit: 879ced2bab1ba95e98fac56c9503791183bc7cbb iommupt: Add the AMD IOMMU v1 page table format
date:   6 months ago
config: um-randconfig-r134-20260514 (https://download.01.org/0day-ci/archive/20260514/202605141052.09y2OBtB-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260514/202605141052.09y2OBtB-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
| Fixes: 879ced2bab1b ("iommupt: Add the AMD IOMMU v1 page table format")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605141052.09y2OBtB-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   drivers/iommu/generic_pt/fmt/iommu_amdv1.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 (ffffffffff000 becomes fffff000)
   include/linux/bitops.h:278:16: sparse: sparse: cast truncates bits from constant value (ffffffffff000 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 <swhiteho@redhat.com>
:::::: CC: Steven Whitehouse <swhiteho@redhat.com>

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