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

[Harald Freudenberger <freude@linux.ibm.com>]

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@linux.ibm.com>
>>> ---
>>> v1:
>>> https://lore.kernel.org/linux-s390/20260806190223.3292580-1- 
>>> iii@linux.ibm.com/
>>> 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 */