From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [RFC 19/19] s390/facilities: enable AP facilities needed by guest Date: Tue, 5 Dec 2017 10:14:15 -0500 Message-ID: References: <1507916344-3896-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1507916344-3896-20-git-send-email-akrowiak@linux.vnet.ibm.com> <20171016112510.39e9c330@mschwideX1> <3e836f59-3ef1-57d8-d6df-b66011c173c4@de.ibm.com> <6d9ae0c1-6f64-1562-bf10-864cf66e3a08@de.ibm.com> <40cdab64-9eeb-02bd-f260-80e9da8c9034@linux.vnet.ibm.com> <35f17b01-49e0-eafb-ad05-c642c579dd3a@de.ibm.com> <8c8c7a0e-2ae4-443b-9444-e2022436c3ee@linux.vnet.ibm.com> <20171205150421.01ec1ed8.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Pierre Morel , Cornelia Huck , Harald Freudenberger Cc: Christian Borntraeger , Martin Schwidefsky , freude@de.ibm.com, mjrosato@linux.vnet.ibm.com, pasic@linux.vnet.ibm.com, Boris Fiuczynski , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, heiko.carstens@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, alifm@linux.vnet.ibm.com, qemu-s390x@nongnu.org, jjherne@linux.vnet.ibm.com, thuth@redhat.com List-ID: On 12/05/2017 09:23 AM, Pierre Morel wrote: > On 05/12/2017 15:04, Cornelia Huck wrote: >> On Tue, 5 Dec 2017 08:52:57 +0100 >> Harald Freudenberger 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 theI think >>>> STFLE.12 >>>> 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 > > So for my point of view, it make sense to separate the three > facilities to enable migration on older syste In the interest of keeping things simple, this makes sense. > > > Pierre > >