From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v4 3/7] s390: zcrypt: driver callback to indicate resource in use References: <1560454780-20359-1-git-send-email-akrowiak@linux.ibm.com> <1560454780-20359-4-git-send-email-akrowiak@linux.ibm.com> <20190618182558.7d7e025a.cohuck@redhat.com> <2366c6b6-fd9e-0c32-0e9d-018cd601a0ad@linux.ibm.com> <20190701212643.0dd7d4ab.cohuck@redhat.com> <20190709124920.3a910dca.cohuck@redhat.com> From: Tony Krowiak Message-ID: <089663dd-2e6d-cbb7-c1ef-a8a4b325abd3@linux.ibm.com> Date: Tue, 9 Jul 2019 17:11:20 -0400 MIME-Version: 1.0 In-Reply-To: <20190709124920.3a910dca.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: To: Cornelia Huck Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, david@redhat.com, mjrosato@linux.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, pmorel@linux.ibm.com, pasic@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com On 7/9/19 6:49 AM, Cornelia Huck wrote: > On Mon, 8 Jul 2019 10:27:11 -0400 > Tony Krowiak wrote: > >> On 7/1/19 3:26 PM, Cornelia Huck wrote: >>> On Wed, 19 Jun 2019 09:04:18 -0400 >>> Tony Krowiak wrote: > >>>> Allow me to first address your fear that a bad actor can hog >>>> resources that can't be removed by root. With this enhancement, >>>> there is nothing preventing a root user from taking resources >>>> from a matrix mdev, it simply forces him/her to follow the >>>> proper procedure. The resources to be removed must first be >>>> unassigned from the matrix mdev to which they are assigned. >>>> The AP bus's /sys/bus/ap/apmask and /sys/bus/ap/aqmask >>>> sysfs attributes can then be edited to transfer ownership >>>> of the resources to zcrypt. >>> >>> What is the suggested procedure when root wants to unbind a queue >>> device? Find the mdev using the queue (is that easy enough?), unassign >>> it, then unbind? Failing to unbind is a bit unexpected; can we point >>> the admin to the correct mdev from which the queue has to be removed >>> first? >> >> The proper procedure is to first unassign the adapter, domain, or both >> from the mdev to which the APQN is assigned. The difficulty in finding >> the queue depends upon how many mdevs have been created. I would expect >> that an admin would keep records of who owns what, but in the case he or >> she doesn't, it would be a matter of printing out the matrix attribute >> of each mdev until you find the mdev to which the APQN is assigned. > > Ok, so the information is basically available, if needed. > >> The only means I know of for informing the admin to which mdev a given >> APQN is assigned is to log the error when it occurs. > > That might be helpful, if it's easy to do. > >> I think Matt is >> also looking to provide query functions in the management tool on which >> he is currently working. > > That also sounds helpful. > > (...) > >>>> * It forces the use of the proper procedure to change ownership of AP >>>> queues. >>> >>> This needs to be properly documented, and the admin needs to have a >>> chance to find out why unbinding didn't work and what needs to be done >>> (see my comments above). >> >> I will create a section in the vfio-ap.txt document that comes with this >> patch set describing the proper procedure for unbinding queues. Of >> course, we'll make sure the official IBM doc also more thoroughly >> describes this. > > +1 for good documentation. > > With that, I don't really object to this change. Then I will make the suggested changes and post v5 to the list. >