Re: [Qemu-devel] [PATCH v2 3/8] s390x: improve error handling for SSCH and RSCH

[Halil Pasic]

On 10/10/2017 03:07 PM, Cornelia Huck wrote:
> On Wed,  4 Oct 2017 17:41:39 +0200
> Halil Pasic <address@hidden> wrote:
> 
>> Simplify the error handling of the SSCH and RSCH handler avoiding
>> arbitrary and cryptic error codes being used to tell how the instruction
>> is supposed to end.  Let the code detecting the condition tell how it's
>> to be handled in a less ambiguous way.  It's best to handle SSCH and RSCH
>> in one go as the emulation of the two shares a lot of code.
>>
>> For passthrough this change isn't pure refactoring, but changes the
>> way kernel reported EFAULT is handled. After clarifying the kernel
>> interface we decided that EFAULT shall be mapped to unit exception.
>> Same goes for unexpected error codes.
>>
>> Signed-off-by: Halil Pasic <address@hidden>
>> ---
>>
>> AFAIR we decided in the previous round to rather do transformation
>> and fixing in one patch than touch stuff twice. Hence this patch
>> ain't pure transformation any more.
>> ---
>>  hw/s390x/css.c              | 83 
>> +++++++++++++--------------------------------
>>  hw/s390x/s390-ccw.c         | 11 +++---
>>  hw/vfio/ccw.c               | 30 ++++++++++++----
>>  include/hw/s390x/css.h      | 24 +++++++++----
>>  include/hw/s390x/s390-ccw.h |  2 +-
>>  target/s390x/ioinst.c       | 53 ++++-------------------------
>>  6 files changed, 77 insertions(+), 126 deletions(-)
> 
> After browsing through this patch, I think the change will work just as
> well if you use e.g. #defines instead of the structure, won't it?
> 

Sure. We just loose type safety. For example if someone ever should try to
propagate a normal errno via return do_something() the compiler won't
catch it we effectively use int for both.