linux-kernel - Re: [PATCH 2/2] s390/vfio-ap: replace open coded locks for VFIO_GROUP_NOTIFY_SET

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Message-ID: <20210728214257.5e5c28c4.pasic@linux.ibm.com>
Date:   Wed, 28 Jul 2021 21:42:57 +0200
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, borntraeger@...ibm.com,
        cohuck@...hat.com, pasic@...ux.vnet.ibm.com, jjherne@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com, david@...hat.com,
        pbonzini@...hat.com, frankja@...ux.ibm.com, imbrenda@...ux.ibm.com
Subject: Re: [PATCH 2/2] s390/vfio-ap: replace open coded locks for
 VFIO_GROUP_NOTIFY_SET_KVM notification

On Wed, 28 Jul 2021 09:43:03 -0400
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> This solution was suggested by Jason G and it does in fact resolve
> the lockdep splat encountered when starting an SE guest with
> access to crypto resources. There is a chance that the KVM lock
> can get held while waiting for the lock on the matrix_dev->mutex,
> but this does not seem like a grave concern to me. 

Yes I agree. I was thinking along the lines: matrix modifications
via the sysfs take the matrix_dev->lock so the level of contention
may depend on what userspace is doing...

Regards,
Halil