Re: [Qemu-devel] [PATCH 3/9] s390x/css: be more consistent if broken beyond repair

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 30 Aug 2017 18:36:03 +0200
Halil Pasic <pasic@linux.vnet.ibm.com> wrote:

> If we detect that the internally manged state of the subchannel
> is broken beyond repair while in do_subchannel_work in case of
> virtual we just abort the operation and pretend all went well,
> while in case of pass-through we honor the situation with -ENODEV
> which results in cc 3 for the instruction whose handler triggered
> the call.
> 
> Let's be consistent on this and do the -ENODEV also for virtual
> subchannels.
> 
> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> Acked-by: Pierre Morel<pmorel@linux.vnet.ibm.com>
> ---
>  hw/s390x/css.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> index 0822538cde..bc47bf5b20 100644
> --- a/hw/s390x/css.c
> +++ b/hw/s390x/css.c
> @@ -1078,7 +1078,7 @@ int do_subchannel_work_virtual(SubchDev *sch)
>          sch_handle_start_func_virtual(sch);
>      } else {
>          /* Cannot happen. */
> -        return 0;
> +        return -ENODEV;

No, this _really_ cannot happen. fctl is a three-bit field, which means
that one of the branches above must have executed. fctl cannot be 0, as
any caller of do_subchannel_work() either sets a bit there or, in the
case of rsch, checks for a bit already set. This is an internal error,
so an assert seems more suitable here. [We might need to keep the
return to keep mingw happy.]

>      }
>      css_inject_io_interrupt(sch);
>      return 0;