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From: Cornelia Huck <cohuck@redhat.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
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
Subject: Re: [PATCH v4 3/7] s390: zcrypt: driver callback to indicate resource in use
Date: Tue, 9 Jul 2019 12:49:20 +0200
Message-ID: <20190709124920.3a910dca.cohuck@redhat.com> (raw)
In-Reply-To: <c771961d-f840-fe8a-09b7-a11b39a74d4c@linux.ibm.com>

On Mon, 8 Jul 2019 10:27:11 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> On 7/1/19 3:26 PM, Cornelia Huck wrote:
> > On Wed, 19 Jun 2019 09:04:18 -0400
> > Tony Krowiak <akrowiak@linux.ibm.com> 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.

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-13 19:39 [PATCH v4 0/7] s390: vfio-ap: dynamic configuration support Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 1/7] s390: vfio-ap: Refactor vfio_ap driver probe and remove callbacks Tony Krowiak
2019-06-17  8:27   ` Harald Freudenberger
2019-06-17 14:24     ` Tony Krowiak
2019-06-18 16:14   ` Cornelia Huck
2019-06-19 12:31     ` Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 2/7] s390: vfio-ap: wait for queue empty on queue reset Tony Krowiak
2019-06-17  8:47   ` Harald Freudenberger
2019-06-17 14:29     ` Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 3/7] s390: zcrypt: driver callback to indicate resource in use Tony Krowiak
2019-06-17  9:28   ` Harald Freudenberger
2019-06-17 14:37     ` Tony Krowiak
2019-06-18 16:25   ` Cornelia Huck
2019-06-19 13:04     ` Tony Krowiak
2019-06-26 21:13       ` Tony Krowiak
2019-06-27  7:25         ` Cornelia Huck
2019-06-27 12:59           ` Tony Krowiak
2019-07-01 19:26       ` Cornelia Huck
2019-07-08 14:27         ` Tony Krowiak
2019-07-09 10:49           ` Cornelia Huck [this message]
2019-07-09 21:11             ` Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 4/7] s390: vfio-ap: implement in-use callback for vfio_ap driver Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 5/7] s390: vfio-ap: allow assignment of unavailable AP resources to mdev device Tony Krowiak
2019-06-17 10:05   ` Harald Freudenberger
2019-06-17 15:07     ` Tony Krowiak
2019-06-18  6:49       ` Harald Freudenberger
2019-06-19 13:39         ` Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 6/7] s390: vfio-ap: allow hot plug/unplug of AP resources using " Tony Krowiak
2019-06-13 19:39 ` [PATCH v4 7/7] s390: vfio-ap: update documentation Tony Krowiak
2019-06-17 11:42   ` Harald Freudenberger
2019-06-17 15:21     ` Tony Krowiak
2019-07-09 15:30 ` [PATCH v4 0/7] s390: vfio-ap: dynamic configuration support Halil Pasic

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