Re: [Qemu-devel] [qemu-s390x] [RFC 14/15] s390-bios: Support booting from real dasd device

[Halil Pasic]

On 07/18/2018 01:35 PM, Cornelia Huck wrote:
> > So to translate the new stuff we would actually have to stop the channel
> > program and resubmit the rest (either by suspend+resume or by break
> > chaining+ssch). The problem with that an execution of a channel program
> > that is composed of four ccws A,B,C,D and an execution of a channel
> > programs composed of ccws A,B immediately followed by and execution
> > of a channel program composed of the ccws C,D is not the same. I.e. it
> > is not generally safe to break a chain of ccws.
> Exploiting suspending would have been my idea. Probably combined with a
> new interface that fetches ccw-by-ccw.
>
> But I don't think it makes sense to spend time thinking about this
> right now.

IMHO exploiting suspending won't work, because the rsch starts a new
chain. If the suspend is a part of the original program the author
of it is responsible to make sure this ain't a problem. But if we
start setting the suspend flag ourselves, we may end up in trouble.

Regards,
Halil