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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 11 Jun 2018 08:51:54 -0400 Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5BCpqWM16777592 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 11 Jun 2018 12:51:52 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A6C9E112061; Mon, 11 Jun 2018 08:51:50 -0400 (EDT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 014A5112063; Mon, 11 Jun 2018 08:51:49 -0400 (EDT) Received: from oc8043147753.ibm.com (unknown [9.85.207.139]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 11 Jun 2018 08:51:48 -0400 (EDT) Subject: Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback To: Halil Pasic , pmorel@linux.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org 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, Janosch Frank 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> <010679ed-bd80-42f8-3f6f-e4dee10e82f5@linux.ibm.com> From: Tony Krowiak Date: Mon, 11 Jun 2018 08:50:49 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18061112-0040-0000-0000-0000043E7060 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009170; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000265; SDB=6.01045401; UDB=6.00535309; IPR=6.00824380; MB=3.00021579; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-11 12:51:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18061112-0041-0000-0000-0000084477BC Message-Id: <4f5f17f1-48ab-6f1e-6ef2-3741fc39e5f4@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-11_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=983 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806110151 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/11/2018 07:32 AM, Halil Pasic wrote: > > > On 06/11/2018 11:23 AM, Pierre Morel wrote: >> 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. >> > > > Pierre's proposal makes a lot of sense to me. We would not need to take > the kvm_lock (which we need to traverse the vm_list safely) for the > validation, and we could have immediate validation (which is in my > opinion > better). > > Also your refcount (which is not a refcout) could go away. You simply > traverse your list and check for duplicates when hooking up the mdev > with KVM. > > And my opinion is if we don't have to add code to the kvm module we > better not. > > @Janosch: Does core KVM share my opinion? Okay, I'll make the change. > > > Regards, > Halil