From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 9 Jul 2019 12:49:20 +0200 From: Cornelia Huck Subject: Re: [PATCH v4 3/7] s390: zcrypt: driver callback to indicate resource in use Message-ID: <20190709124920.3a910dca.cohuck@redhat.com> In-Reply-To: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: To: Tony Krowiak 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 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.