On 17.02.2018 09:11, Thomas Huth wrote: [...] > > I still think that the information should *not* be stored within the > IplParameterBlock to avoid that we pass it via DIAG 0x308, too. > If we do it like this, I'm pretty sure that we will look at this code in > a couple of years and wonder whether we can change it again or whether > this is an established interface between the host and the guest. So > please, let's avoid establishing such "hidden" interfaces just out of > current convenience. There must be a better location for this. > Christian, do you have an idea? > > Thomas > In principle I do agree, although I think we can manage the host/guest boundary. If we believe we can't, we have a much bigger problem (looking at the position of the iplb smack in the middle of the s390-ipl state).
The main reason why I didn't bother to introduce a new private field in s390-ipl was that I expect more changes to the IPL area in the future (earlier than in a couple of years) and am not really sure whether this QEMU <-> BIOS interface will remain the same and how much effort to spend on it. The major point of this change is to move non-standard data out of the guest-visible IPLB to avoid compatibility problems in the future, while still catering for features like network boot and boot menus. I have no bias against other solutions achieving this objective. If you and Christian think we need a new field, it's all right with me. -- Regards, Viktor Mihajlovski