linux-kernel - Re: [PATCH v4 3/7] s390: ap: associate a ap_vfio

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Date:   Wed, 27 Feb 2019 10:32:11 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, akrowiak@...ux.ibm.com,
        pasic@...ux.ibm.com, david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v4 3/7] s390: ap: associate a ap_vfio_queue and a matrix
 mdev

On Fri, 22 Feb 2019 16:29:56 +0100
Pierre Morel <pmorel@...ux.ibm.com> wrote:

> We need to associate the ap_vfio_queue, which will hold the
> per queue information for interrupt with a matrix mediated device
> which hold the configuration and the way to the CRYCB.
> 
> Let's do this when assigning a APID or a APQI to the mediated device
> and clear the relation when unassigning.
> 
> Queuing the devices on a list of free devices and testing the
> matrix_mdev pointer to the associated matrix allow us to know
> if the queue is associated to the matrix device and associated
> or not to a mediated device.
> 
> When resetting an AP queue we must wait until there are no more
> messages in the message queue before considering the queue is really
> in a clean state.
> 
> Let's do it and wait until the status response code indicate the
> queue is empty after issuing a PAPQ/ZAPQ instruction.

I'm a bit confused about the context where that list moving etc. is
supposed to take place.

When are we assigning/deassigning? Is there even supposed to be any
activity that we need to zap on the queues?

Do we need any serialization/locking on the lists?

> 
> Being at work on the reset function, let's simplify
> vfio_ap_mdev_reset_queue and vfio_ap_mdev_reset_queues by using the
> vfio_ap_queue structure as parameter.
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 385 +++++++++++++++++++-------------------
>  1 file changed, 189 insertions(+), 196 deletions(-)