From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [PATCH v5 10/13] s390: vfio-ap: sysfs interface to view matrix mdev matrix Date: Thu, 7 Jun 2018 08:53:20 -0400 Message-ID: <525163cf-d656-b146-05b6-2efbbd2f5a9d@linux.vnet.ibm.com> References: <1525705912-12815-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1525705912-12815-11-git-send-email-akrowiak@linux.vnet.ibm.com> <53275110-45fb-d50f-c97e-93141378f094@linux.vnet.ibm.com> <89bda651-d465-af50-a737-1900a54b01c8@linux.ibm.com> <6f67a282-773d-3fca-5b36-cc23ad49ba5b@linux.vnet.ibm.com> <32340d2a-bea6-bdb1-38a6-76afe3d54672@linux.ibm.com> <624dcbbf-5f40-6f27-b173-a4c533dd7781@linux.vnet.ibm.com> <4f42fa11-e9cc-20a9-3068-b103a8ead644@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4f42fa11-e9cc-20a9-3068-b103a8ead644@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: 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 List-ID: On 06/06/2018 11:10 AM, Pierre Morel wrote: > On 06/06/2018 16:24, Tony Krowiak wrote: >> On 06/05/2018 08:40 AM, Pierre Morel wrote: >>> On 30/05/2018 16:28, Tony Krowiak wrote: >>>> On 05/24/2018 05:10 AM, Pierre Morel wrote: >>>>> On 23/05/2018 16:38, Tony Krowiak wrote: >>>>>> On 05/16/2018 03:55 AM, Pierre Morel wrote: >>>>>>> On 07/05/2018 17:11, Tony Krowiak wrote: >>>>>>>> Provides a sysfs interface to view the AP matrix configured for >>>>>>>> the >>>>>>>> mediated matrix device. >>>>>>>> >>>>>>>> The relevant sysfs structures are: >>>>>>>> >>>>>>>> /sys/devices/vfio_ap >>>>>>>> ... [matrix] >>>>>>>> ...... [mdev_supported_types] >>>>>>>> ......... [vfio_ap-passthrough] >>>>>>>> ............ [devices] >>>>>>>> ...............[$uuid] >>>>>>>> .................. matrix >>>>>>>> >>>>>>>> To view the matrix configured for the mediated matrix device, >>>>>>>> print the matrix file: >>>>>>> >>>>>>> This is the configured matrix, not the one used by the guest. >>>>>>> Nothing in the patches protect against binding a queue and >>>>>>> assigning >>>>>>> a new AP when the guest runs. >>>>>>> The card and queue will be showed by this entry. >>>>>> >>>>>> Of course, as stated above, this is the matrix configured for the >>>>>> mediated matrix device. Are you suggesting here that the driver >>>>>> should prevent assigning a new adapter or domain while a guest is >>>>>> running? Couldn't this be a step in the process for hot (un)plugging >>>>>> AP queues? >>>>> >>>>> No, I mean what is the point to show this? >>>>> It is not what the guest sees. >>>>> Has it any use case? >>>> >>>> The point is to display the matrix so one can view the AP queues that >>>> have been assigned to the mediated matrix device. This is the only way >>>> to view the matrix. Do you not find value in being able to see what >>>> has been assigned to the mediated matrix device? >>> >>> Two things: >>> 1) I think it is better to retrieve the individual masks >> >> I am not certain what you mean by this. Are you suggesting we display >> the >> actual mask? For example, the APM: >> >> 08000000000000001000000000000c0000000030000000000800000000000001 >> >> If that is the case, I completely disagree as that would be worthless >> from >> a user perspective. Trying to figure out which APs are configured >> would be >> ridiculously complicated. > > - It is compatible with what the AP BUS shows > - a cut and past is easy > - you can use a userland script to translate to another format > >> >> Or, are you suggesting something like this: >> >> 4,67,116,117,154,155,255 > > - this is not compatible with what the AP BUS shows > - as in the first case this is easy to parse > > Both propositions look better to me. > >> >> Personally, I found viewing the queues to be much more valuable when >> configuring the mediated device's matrix. I originally displayed the >> individual adapter and domain attributes and found it cumbersome to >> mentally configure what the matrix looked like. If you think of the >> lszcrypt command, it outputs the adapters and queues which is the model >> I used for this. > > what is the point of seeing what the matrix looks like ? > It is interesting for the developer not for the administrator. > What the administrator needs is: > - To assign AP and to see what has been assigned > - To assign domains and to see what has been assigned > >> >>> 2) As I said above, what you show is not the effective mask used by >>> the guest >> >> Why would a sysfs attribute for the mediated matrix device show the >> effective >> mask used by the guest? > > OK, bad word, "effective", replace with "really". > > We do not implement any kind of provisioning nor do we implement update > of the CRYCB at any point after the first mediated device open. I think this is a way we might be able to hot plug/unplug devices. > > > Binding a queue and updating the mask can be done at any time (may be > we should change this ?) As I said above, I think we can utilize this as a means of hot plugging/unplugging AP adapters and domains. If the guest is running when an adapter or domain is assigned, we can update the guest's CRYCB at that time. > > > What is the point of showing a matrix which will never be used by the > guest? That is simply not true. The matrix WILL be used by a guest the next time a guest is configured with a vfio-ap device referencing the path to the mediated matrix device - i.e., -device vfio-ap,sysfsdev=$PATH. The point is to show the matrix assigned to the mediated matrix device. In my mind, the mediated matrix device is a separate object from the guest. Sure it is used to configure a guest's matrix when the guest is started, but it could be used to configure the matrix for any guest; it has no direct connection to a particular guest until a guest using the device is started. IMHO the sysfs attributes for the mediated matrix device reflect only the attributes of the device, not the attributes of a guest. > > > > >> >>> >>> >>> >>> >>> >> >