From mboxrd@z Thu Jan 1 00:00:00 1970 From: Harald Freudenberger Subject: Re: [PATCH v6 21/21] s390: doc: detailed specifications for AP virtualization Date: Tue, 3 Jul 2018 09:46:54 +0200 Message-ID: <6a330cae-2fe2-54df-edce-c3360117cf3c@linux.ibm.com> References: <1530306683-7270-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1530306683-7270-22-git-send-email-akrowiak@linux.vnet.ibm.com> <49b11ac2-2230-ad74-1583-c6a57f8b31e3@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 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, Tony Krowiak To: Halil Pasic , Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: <49b11ac2-2230-ad74-1583-c6a57f8b31e3@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 02.07.2018 18:28, Halil Pasic wrote: > > > On 06/29/2018 11:11 PM, Tony Krowiak wrote: >> This patch provides documentation describing the AP architecture and >> design concepts behind the virtualization of AP devices. It also >> includes an example of how to configure AP devices for exclusive >> use of KVM guests. >> >> Signed-off-by: Tony Krowiak >> --- > [..] >> + >> +Reserve APQNs for exclusive use of KVM guests >> +--------------------------------------------- >> +The following block diagram illustrates the mechanism by which APQNs are >> +reserved: >> + >> +                              +------------------+ >> +                 remove       |                  |   unbind >> +         +------------------->+ cex4queue driver +<-----------+ >> +         |                    |                  |            | >> +         |                    +------------------+            | >> +         |                                                    | >> +         |                                                    | >> +         |                                                    | >> ++--------+---------+ register +------------------+      +-----+------+ >> +|                  +<---------+                  | bind |            | >> +|      ap_bus      |          |  vfio_ap driver  +<-----+    admin   | >> +|                  +--------->+                  |      |            | >> ++------------------+  probe   +---+--------+-----+      +------------+ >> +                                  |        | >> +                           create |        | store APQN >> +                                  |        | >> +                                  v        v >> +                              +---+--------+-----+ >> +                              |                  | >> +                              |  matrix device   | >> +                              |                  | >> +                              +------------------+ >> + >> +The process for reserving an AP queue for use by a KVM guest is: >> + >> +* The vfio-ap driver during its initialization will perform the following: >> +  * Create the 'vfio_ap' root device - /sys/devices/vfio_ap >> +  * Create the 'matrix' device in the 'vfio_ap' root >> +  * Register the matrix device with the device core >> +* Register with the ap_bus for AP queue devices of type 10 devices (CEX4 and >> +  newer) and to provide the vfio_ap driver's probe and remove callback >> +  interfaces. The reason why older devices are not supported is because there >> +  are no systems available on which to test. >> +* The admin unbinds queue cc.qqqq from the cex4queue device driver. This results >> +  in the ap_bus calling the the device driver's remove interface which >> +  unbinds the cc.qqqq queue device from the driver. > > What if the queue cc.qqqq is already in use? AFAIU unbind is almost as radical as > pulling a cable. What is the proper procedure an admin should follow before doing > the unbind? What do you mean on this level with 'in use'? A unbind destroys the association between device and driver. There is no awareness of 'in use' or 'not in use' on this level. This is a hard unbind. > >> +* The admin binds the cc.qqqq queue to the vfio_ap device driver. This results >> +  in the ap_bus calling the device vfio_ap driver's probe interface to bind >> +  queue cc.qqqq to the driver. The vfio_ap device driver will store the APQN for >> +  the queue in the matrix device >> + > [..] > > -- > To unsubscribe from this list: send the line "unsubscribe linux-s390" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html >