ambiguous instructions require an explicit suffix
As of version 2.35, the GNU assembler has gained a new class of warnings about instructions where the size of the operand is ambiguous and cannot be inferred. They look like:
../../i86pc/ml/locore.s:187: Warning: no instruction mnemonic suffix given and no register operands; using default for `bts'
There are a few places in the kernel where this occurs around
bt[s] instructions; they need updating with an explicit suffix
In some cases, the existing assumed operand size may also not be correct, resulting in real bugs.