On Wed, 18 Oct 2017 11:52:03 +0200 Thomas Huth <th...@redhat.com> wrote:
> On 18.10.2017 11:30, Thomas Huth 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> > [...] > >> @@ -71,10 +71,24 @@ again: > >> goto again; > >> } > >> error_report("vfio-ccw: wirte I/O region failed with errno=%d", > >> errno); > >> - return -errno; > >> + ret = -errno; > >> + } else { > >> + ret = region->ret_code; > >> + } > >> + switch (-ret) { > >> + case 0: > >> + return IOINST_CC_EXPECTED; > >> + case EBUSY: > >> + return IOINST_CC_BUSY; > >> + case ENODEV: > >> + case EACCES: > >> + return IOINST_CC_NOT_OPERATIONAL; > >> + case EFAULT: > >> + default: > >> + sch_gen_unit_exception(sch); > >> + css_inject_io_interrupt(sch); > >> + return IOINST_CC_EXPECTED; > > > > Do we feel really confident that it is OK to do the setcc() in case of > > an exception here later? ... otherwise it might be necessery to > > introduce something like IOINST_EXCEPTION to the enum to signal the > > ioinst_handle_xxx() callers that they should not do the setcc() anymore... > > ... or maybe rather at least return IOINST_CC_STATUS_PRESENT instead? > IOINST_CC_EXPECTED sounds somewhat wrong to me here. But the ssch did conclude as expected :) Keep in mind that QEMU performs the start function synchronously (i.e., before the condition code is set). On real hardware, you get a cc 0 for the ssch if the subchannel is basically in a status that's ok for triggering the start function. A unit exception is a possible result of the start function (and therefore generating an I/O interrupt, which you only get if ssch set cc 0.)