From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback Date: Mon, 11 Jun 2018 11:23:27 +0200 Message-ID: <010679ed-bd80-42f8-3f6f-e4dee10e82f5@linux.ibm.com> References: <1525705912-12815-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1525705912-12815-12-git-send-email-akrowiak@linux.vnet.ibm.com> <98ea7ce2-2539-e2ff-4bb4-297e784d87bd@linux.ibm.com> <7bb480ac-5723-83ff-c797-53c1ab0458c1@linux.vnet.ibm.com> <93cd0f46-a410-51c8-00b9-810c1b3d3ae2@linux.ibm.com> <0f37dc39-7355-19e5-40c9-a02a1ea58c2d@linux.vnet.ibm.com> <736a1346-f81a-7f71-7d13-38729ff78e4f@linux.ibm.com> <8f68183d-8385-8025-1898-23cad604ae94@linux.vnet.ibm.com> <9e30c9b0-a04c-0c4e-9d3d-37e7a53a7f72@linux.ibm.com> <5f9c3f97-34e2-bf68-b8ca-ac9288ea5efa@linux.vnet.ibm.com> Reply-To: pmorel@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com To: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/06/2018 23:59, Tony Krowiak wrote: > On 06/07/2018 01:15 PM, Pierre Morel wrote: >> ...snip... >>>> >>>>> >>>>> Why maintain a list of kvm_ap_matrix structures if we don't have >>>>> to; it is stored >>>>> with the mediated matrix device which is passed in to all of the >>>>> vfio_ap driver >>>>> callbacks. >>>> >>>> Because using the vm_list which is a static in kvm makes you stick >>>> inside the kvm code. > > I understand your point here, but even if we did maintain a list of > kvm_ap_matrix structures, > we still need the kvm code to configure the guest's CRYCB and > eventually ECA.28. There is > also code in kvm-ap.c that is called from KVM. The only code from kvm-ap which is called from KVM is temporary code waiting for Harald to offer the clean interface to AP instructions. > The idea behind kvm-ap.c is that all code > related to configuration of AP structures in KVM is in this one spot. This I understand, but the code can be in one spot inside VFIO_AP instead of inside KVM. Putting the code inside KVM induce dependencies between KVM and AP while the kvm/vfio interface allows to avoid this dependency. The purpose of VFIO_AP is to handle the CRYCB, all get/clear/set crycb masks functions should be in VFIO AP. If we use wrappers in KVM, since the CRYCB is an a SIE extension, it is legitimate, the KVM interface to the CRYCB should only handle bitmaps and be unaware of the vfio_ap internal structures. Another concern, the kvm_ap_validate_queue_sharing() should not be inside KVM because it is a decision of current VFIO_AP driver to not share the queues between guest of level 2. The Z architecture does not allow to share AP queues between guests of level 1 but we could re-engineer the AP bus and the ' VFIO AP to offer queue sharing for guest level 2. This would be a new VFIO_AP driver (and an AP bus extension). We should not have to change KVM for this. Regards, Pierre > >> >> >> > -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany