On 10/18/2017 12:07 PM, Thomas Huth wrote:
> On 18.10.2017 11:52, Cornelia Huck wrote:
>> On Wed, 18 Oct 2017 11:30:47 +0200
>> Thomas Huth <th...@redhat.com> wrote:
>>
>>> On 17.10.2017 16:04, Halil Pasic 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 and absence of required ORB flags.
>>>>
>>>> Signed-off-by: Halil Pasic <pa...@linux.vnet.ibm.com>
>>>> ---
>>>> hw/s390x/css.c | 84
>>>> +++++++++++++--------------------------------
>>>> hw/s390x/s390-ccw.c | 11 +++---
>>>> hw/vfio/ccw.c | 28 +++++++++++----
>>>> include/hw/s390x/css.h | 23 +++++++++----
>>>> include/hw/s390x/s390-ccw.h | 2 +-
>>>> target/s390x/ioinst.c | 53 ++++------------------------
>>>> 6 files changed, 75 insertions(+), 126 deletions(-)
>>>>
>>>> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
>>>> index aa233d5f8a..ff5a05c34b 100644
>>>> --- a/hw/s390x/css.c
>>>> +++ b/hw/s390x/css.c
>>>> @@ -1181,12 +1181,11 @@ static void sch_handle_start_func_virtual(SubchDev
>>>> *sch)
>>>>
>>>> }
>>>>
>>>> -static int sch_handle_start_func_passthrough(SubchDev *sch)
>>>> +static IOInstEnding sch_handle_start_func_passthrough(SubchDev *sch)
>>>> {
>>>>
>>>> PMCW *p = &sch->curr_status.pmcw;
>>>> SCSW *s = &sch->curr_status.scsw;
>>>> - int ret;
>>>>
>>>> ORB *orb = &sch->orb;
>>>> if (!(s->ctrl & SCSW_ACTL_SUSP)) {
>>>> @@ -1200,31 +1199,12 @@ static int
>>>> sch_handle_start_func_passthrough(SubchDev *sch)
>>>> */
>>>> if (!(orb->ctrl0 & ORB_CTRL0_MASK_PFCH) ||
>>>> !(orb->ctrl0 & ORB_CTRL0_MASK_C64)) {
>>>> - return -EINVAL;
>>>> + warn_report("vfio-ccw requires PFCH and C64 flags set...");
>>>
>>> Not sure, but should this maybe rather be a
>>> "qemu_log_mask(LOG_GUEST_ERROR, ...)" instead?
>>
>> Is that visible by default, though? I'd rather want the admin to be
>> able to find a hint in a log somewhere why the guest I/O is rejected.
>
> Well, the guest could also trigger this condition on purpose (e.g.
> kvm-unit-tests), so I wonder whether we want to see the warning in that
> case, too...
> IMHO this is exactly what qemu_log_mask(LOG_GUEST_ERROR, ...) has been
> implemented for: Log errors from the guest in case you suspect that the
> guest is doing something wrong. But that's just my 0.02 €, feel free to
> ignore me.
>
>>>> @@ -1844,27 +1816,23 @@ void css_do_schm(uint8_t mbk, int update, int dct,
>>>> uint64_t mbo)
>>>> }
>>>> }
>>>>
>>>> -int css_do_rsch(SubchDev *sch)
>>>> +IOInstEnding css_do_rsch(SubchDev *sch)
>>>> {
>>>> SCSW *s = &sch->curr_status.scsw;
>>>> PMCW *p = &sch->curr_status.pmcw;
>>>> - int ret;
>>>>
>>>> if (~(p->flags) & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA)) {
>>>> - ret = -ENODEV;
>>>> - goto out;
>>>> + return IOINST_CC_NOT_OPERATIONAL;
>>>> }
>>>>
>>>> if (s->ctrl & SCSW_STCTL_STATUS_PEND) {
>>>> - ret = -EINPROGRESS;
>>>> - goto out;
>>>> + return IOINST_CC_STATUS_PRESENT;
>>>> }
>>>>
>>>> if (((s->ctrl & SCSW_CTRL_MASK_FCTL) != SCSW_FCTL_START_FUNC) ||
>>>> (s->ctrl & SCSW_ACTL_RESUME_PEND) ||
>>>> (!(s->ctrl & SCSW_ACTL_SUSP))) {
>>>> - ret = -EINVAL;
>>>> - goto out;
>>>> + return IOINST_CC_BUSY;
>>>
>>> Why is EINVAL now mapped to IOINST_CC_BUSY? Shouldn't that be
>>> IOINST_CC_STATUS_PRESENT instead?
>>
>> No, that is correct (see the PoP for when cc 2 is supposed to be set by
>> rsch).
>
> So if this is on purpose, this change in behavior should also be
> mentioned in the patch description, I think.
>
No. have a look at the function ioinst_handle_rsch. It used
to map -EINVAL to cc 2 (and was an oddball in this respect) so we
keep the old behavior, it's just more obvious whats happening.
Regards,
Halil
> Thomas
>
