Re: [Qemu-devel] [PATCH v3 7/7] s390x: refactor error handling for MSCH handler

[Halil Pasic <pasic@linux.vnet.ibm.com>]

On 10/18/2017 12:02 PM, Cornelia Huck wrote:
> On Wed, 18 Oct 2017 12:00:05 +0200
> Thomas Huth <thuth@redhat.com> wrote:
> 
>> On 17.10.2017 16:04, Halil Pasic wrote:
>>> Simplify the error handling of the MSCH.  Let the code detecting the
>>> condition tell (in a less ambiguous way) how it's to be handled. No
>>> changes in behavior.  
>>
>> ok, so you claim no changes in behavior ...
>>
>>> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
>>> ---
>>>  hw/s390x/css.c         | 18 +++++-------------
>>>  include/hw/s390x/css.h |  2 +-
>>>  target/s390x/ioinst.c  | 23 ++++-------------------
>>>  3 files changed, 10 insertions(+), 33 deletions(-)
>>>
>>> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
>>> index b9e0329825..30fc236946 100644
>>> --- a/hw/s390x/css.c
>>> +++ b/hw/s390x/css.c
>>> @@ -1347,28 +1347,24 @@ static void copy_schib_from_guest(SCHIB *dest, const SCHIB *src)
>>>      }
>>>  }
>>>  
>>> -int css_do_msch(SubchDev *sch, const SCHIB *orig_schib)
>>> +IOInstEnding css_do_msch(SubchDev *sch, const SCHIB *orig_schib)
>>>  {
>>>      SCSW *s = &sch->curr_status.scsw;
>>>      PMCW *p = &sch->curr_status.pmcw;
>>>      uint16_t oldflags;
>>> -    int ret;
>>>      SCHIB schib;
>>>  
>>>      if (!(sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_DNV)) {
>>> -        ret = 0;
>>> -        goto out;
>>> +        return IOINST_CC_EXPECTED;
>>>      }
>>>  
>>>      if (s->ctrl & SCSW_STCTL_STATUS_PEND) {
>>> -        ret = -EINPROGRESS;
>>> -        goto out;
>>> +        return IOINST_CC_STATUS_PRESENT;
>>>      }
>>>  
>>>      if (s->ctrl &
>>>          (SCSW_FCTL_START_FUNC|SCSW_FCTL_HALT_FUNC|SCSW_FCTL_CLEAR_FUNC)) {
>>> -        ret = -EBUSY;
>>> -        goto out;
>>> +        return IOINST_CC_STATUS_PRESENT;
>>>      }  
>>
>> ... but here you change -EBUSY (which got mapped to CC=2) to
>> CC_STATUS_PRESENT which means CC=1. So that's a change in behavior. i.e.
>> this is either a bug, or you should update the patch description with a
>> justification for this change in behavior.
> 
> Indeed, that's a bug. We still want cc 2.
> 

Agree, it is a bug. It was OK in v1 but was already buggy in
v2.

Conny can you fix this up as well please?

Thanks in advance!

Halil