Re: [qemu-s390x] [Qemu-devel] [PATCH v2 2/3] hw/s390x/css: Remove QEMU_PACKED from struct SenseId

[David Hildenbrand]

>> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
>> index 5a9fe45ce8..db378f6238 100644
>> --- a/hw/s390x/css.c
>> +++ b/hw/s390x/css.c
>> @@ -750,12 +750,13 @@ static void sch_handle_halt_func(SubchDev *sch)
>>
>>  }
>>
>> -static void copy_sense_id_to_guest(SenseId *dest, SenseId *src)
>> +static void copy_sense_id_to_guest(SenseIdPacked *dest, SenseId *src)
>>  {
>>      int i;
>>
>>      dest->reserved = src->reserved;
>> -    dest->cu_type = cpu_to_be16(src->cu_type);
>> +    /* avoid unaligned accesses */
>> +    dest->cu_type[0] = cpu_to_be16(src->cu_type) >> 8;
> 
> The error Peter reported was "load of misaligned address", so the
> culprit is the cpu_to_be16() call. See bswap16s() casting an unaligned u16.
> 
> IMHO your patch should trigger the same issue.

No, src->cu_type would be aligned now ...

> 
> What about this instead?
> 
>       dest->cu_type = lduw_be_p(&src->cu_type);
> 

... however that certainly looks better ...

... but looks like Thomas wants to stick to the handcrafted approach.

Thanks!


-- 

Thanks,

David / dhildenb