On Tue, 5 Dec 2017 15:23:50 +0100 Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> wrote: > On 05/12/2017 15:04, Cornelia Huck wrote: > > On Tue, 5 Dec 2017 08:52:57 +0100 > > Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx> wrote: > > > >> On 12/02/2017 02:30 AM, Tony Krowiak wrote: > > > >>> I agree with your suggestion that defining a new CPU model feature is probably > >>> the best way to resolve this issue. The question is, should we define a single > >>> feature indicating whether AP instructions are installed and set features bits > >>> for the guest based on whether or not they are set in the linux host, or should > >>> we define additional CPU model features for turning features bits on and off? > >>> I guess it boils down to what behavior is expected for the AP bus running on > >>> the linux guest. Here is a rundown of the facilities bits associated with AP > >>> and how they affect the behavior of the AP bus: > >>> > >>> * STFLE.12 indicates whether the AP query function is available. If this bit > >>> is not set, then the AP bus scan will only test domains 0-15. For example, > >>> if adapters 4, 5, and 6 and domains 12 and 71 (0x47) are installed, then AP > >>> queues 04.0047, 05.0047 and 06.0047 will not be made available. > >> STFLE 12 is the indication for Query AP Configuration Information (QCI) available. > >>> * STFLE.15 indicates whether the AP facilities test function is available. If > >>> this bit is not set, then the CEX4, CEX5 and CEX6 device drivers discovered > >>> by the AP bus scan will not get bound to any AP device drivers. Since the > >>> AP matrix model supports only CEX4 and greater, no devices will be bound > >>> to any driver for a guest. > >> This T-Bit extension to the TAPQ subfunction is a must have. When kvm only > >> supports CEX4 and upper then this bit could also act as the indicator for > >> AP instructions available. Of course if you want to implement pure virtual > >> full simulated AP without any real AP hardware on the host this bit can't > >> be the indicator. > > > > It would probably make sense to group these two together. Or is there > > any advantage in supporting only a part of it? > > > >>> * STFLE.65 indicates whether AP interrupts are available. If this bit is not > >>> set, then the AP bus will use polling instead of using interrupt handlers > >>> to process AP events. > > > > So, does this indicate "adapter interrupts for AP" only? If so, we > > should keep this separate and only enable it when we have the gisa etc. > > ready. > > > > Yes, STFLE 65, it is for AP only. > > QCI, STFLE 12, is no present on older systems, in this case AP uses TAPQ > to retrieve information for each AP Dumb question: How old? Machines that are still supported? > > So for my point of view, it make sense to separate the three facilities > to enable migration on older systems. OK, if STFLE 12 might not be present (pending my question above), but STFLE 15 is indeed a must-have, we should split this up. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
