Re: [PATCH] s390/percpu: Fix MVIY_PERCPU() with older binutils

On Wed, Aug 12, 2026 at 10:30:36PM +0200, Karl Mehltretter wrote:
> Commit a737737cdb9c ("s390/percpu: Infrastructure for more efficient
> this_cpu operations") introduced MVIY_PERCPU(), which stringifies
> arguments that are already C string literals. This generates an
> assembler macro invocation with whitespace-separated quoted arguments:
> 
>   GEN_MVIY "459712" "%r3"
> 
> GNU as versions prior to binutils 2.39 drop the separating whitespace
> between quoted macro arguments during input scrubbing. They
> consequently parse the invocation as a single argument and emit
> repeated warnings:
> 
>   Warning: missing closing `"'
> 
> The .ifc in GEN_MVIY never matches and GNU as exits successfully
> without emitting the mviy instruction. As a result, the interrupted
> per-CPU sequence is not marked in lowcore and the exception return
> path cannot repair the per-CPU address register after migration.
> 
> All MVIY_PERCPU() callers pass C string literals. Use them directly
> and separate the assembler macro arguments with an explicit comma. The
> resulting invocation is:
> 
>   GEN_MVIY 459712, %r3
> 
> This form is unambiguous for GNU as and LLVM's integrated assembler.
> This behavior was fixed in GNU as from binutils 2.39, but Linux
> supports binutils 2.30.
> 
> Fixes: a737737cdb9c ("s390/percpu: Infrastructure for more efficient this_cpu operations")
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Karl Mehltretter <[email protected]>
> ---
>  arch/s390/include/asm/percpu.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Thanks a lot. I'm about to change this code anyway. It seems it should better
error out instead of generating incorrect code (even if there is a warning).

Vasily, could you add

Cc: [email protected]

please?

Reviewed-by: Heiko Carstens <[email protected]>