Re: [PATCH v2] s390/cpacf: Unpoison instruction results

[Harald Freudenberger]

On 2026-08-13 16:09, Ilya Leoshkevich wrote:
> On 8/13/26 16:06, Harald Freudenberger wrote:
> > On 2026-08-07 14:20, Ilya Leoshkevich wrote:
> > > Stop KMSAN from complaining about CPACF outputs being uninitialized.
> > >
> > > Do not unpoison variable-length parameter blocks: mapping function
> > > codes (like CPACF_KIMD_SHA_256) to lengths is ugly. Let the callers
> > > handle this once need arises.
> > >
> > > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> > > ---
> > > v1:
> > > https://lore.kernel.org/linux-s390/20260806190223.3292580-1- 
> > > iii@xxxxxxxxxxxxx/
> > > v1 -> v2: Unpoison outputs of more instructions (Sashiko).
> >
> > See my comment below.
> >
> > >  arch/s390/include/asm/cpacf.h | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/arch/s390/include/asm/cpacf.h b/arch/s390/include/asm/ 
> > > cpacf.h
> > > index a83683169d98d..13d6a6344802a 100644
> > > --- a/arch/s390/include/asm/cpacf.h
> > > +++ b/arch/s390/include/asm/cpacf.h
> > > @@ -301,6 +301,7 @@ static __always_inline void 
> > > __cpacf_query(unsigned
> > > int opcode,
> > >                        cpacf_mask_t *mask)
> > >  {
> > >      __cpacf_query_insn(opcode, mask, CPACF_FC_QUERY);
> > > +    kmsan_unpoison_memory(mask, sizeof(*mask));
> > >  }
> > >
> > >  static __always_inline int __cpacf_check_opcode(unsigned int opcode)
> > > @@ -370,6 +371,7 @@ static __always_inline int
> > > cpacf_query_func(unsigned int opcode,
> > >  static __always_inline void __cpacf_qai(unsigned int opcode, 
> > > cpacf_qai_t *qai)
> > >  {
> > >      __cpacf_query_insn(opcode, qai, CPACF_FC_QUERY_AUTH_INFO);
> > > +    kmsan_unpoison_memory(qai, sizeof(*qai));
> > >  }
> > >
> > >  /**
> > > @@ -422,6 +424,7 @@ static inline int cpacf_km(unsigned long func, 
> > > void *param,
> > >            [opc] "i" (CPACF_KM)
> > >          : "cc", "memory", "0", "1");
> > >
> > > +    kmsan_unpoison_memory(dest, src_len - s.odd);
> > >      return src_len - s.odd;
> > >  }
> > >
> > > @@ -454,6 +457,7 @@ static inline int cpacf_kmc(unsigned long func, 
> > > void *param,
> > >            [opc] "i" (CPACF_KMC)
> > >          : "cc", "memory", "0", "1");
> > >
> > > +    kmsan_unpoison_memory(dest, src_len - s.odd);
> > >      return src_len - s.odd;
> > >  }
> > >
> > > @@ -587,6 +591,7 @@ static inline int cpacf_kmctr(unsigned long func,
> > > void *param, u8 *dest,
> > >            [opc] "i" (CPACF_KMCTR)
> > >          : "cc", "memory", "0", "1");
> > >
> > > +    kmsan_unpoison_memory(dest, src_len - s.odd);
> > >      return src_len - s.odd;
> > >  }
> > >
> > > @@ -619,6 +624,7 @@ static inline void cpacf_prno(unsigned long func,
> > > void *param,
> > >          : [fc] "d" (func), [pba] "d" ((unsigned long)param),
> > >            [seed] "d" (s.pair), [opc] "i" (CPACF_PRNO)
> > >          : "cc", "memory", "0", "1");
> > > +    kmsan_unpoison_memory(dest, dest_len);
> > >  }
> > >
> > >  /**
> > > @@ -731,6 +737,7 @@ static inline void cpacf_kma(unsigned long func,
> > > void *param, u8 *dest,
> > >          : [fc] "d" (func), [pba] "d" ((unsigned long)param),
> > >            [opc] "i" (CPACF_KMA)
> > >          : "cc", "memory", "0", "1");
> > > +    kmsan_unpoison_memory(dest, src_len);
> >
> > I am unhappy with this kma thing. This would only work properly with
> > CC 0. But CC 1 and 2 are not handled properly. However, I had a closer
> > look onto the AR for kma and ... well this inline function should
> > handle CC 1 and CC 2 somehow and it should similar to the other inline
> > functions return the number of bytes processed like for example 
> > cpacf_km().
> > I'll open up a bugzilla to fix this kma inline function.
> > If you leave out this kma hunk you can add my R-b.
>
> Will do, thanks!
>
> May I ask you to add a proper KMSAN annotation while fixing CC1/CC2
> cases? Alternatively I can do it myself afterwards, of course.

Yes, I'll do that.

> > >  }
> > >
> > >  #endif    /* _ASM_S390_CPACF_H */