linux-kernel - Re: [PATCH v16 10/14] s390/zcrypt: driver callback to indicate resource in use

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Date:   Thu, 20 May 2021 13:58:04 +0200
From:   Harald Freudenberger <freude@...ux.ibm.com>
To:     Julian Wiedmann <jwi@...ux.ibm.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     jjherne@...ux.ibm.com, borntraeger@...ibm.com, cohuck@...hat.com,
        mjrosato@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com
Subject: Re: [PATCH v16 10/14] s390/zcrypt: driver callback to indicate
 resource in use

On 19.05.21 13:58, Julian Wiedmann wrote:
> On 10.05.21 19:44, Tony Krowiak wrote:
>> Introduces a new driver callback to prevent a root user from unbinding
>> an AP queue from its device driver if the queue is in use. The callback
>> will be invoked whenever a change to the AP bus's sysfs apmask or aqmask
>> attributes would result in one or more AP queues being removed from its
>> driver. If the callback responds in the affirmative for any driver
>> queried, the change to the apmask or aqmask will be rejected with a device
>> busy error.
>>
>> For this patch, only non-default drivers will be queried. Currently,
>> there is only one non-default driver, the vfio_ap device driver. The
>> vfio_ap device driver facilitates pass-through of an AP queue to a
>> guest. The idea here is that a guest may be administered by a different
>> sysadmin than the host and we don't want AP resources to unexpectedly
>> disappear from a guest's AP configuration (i.e., adapters and domains
>> assigned to the matrix mdev). This will enforce the proper procedure for
>> removing AP resources intended for guest usage which is to
>> first unassign them from the matrix mdev, then unbind them from the
>> vfio_ap device driver.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> Reviewed-by: Harald Freudenberger <freude@...ux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>
>> ---
>>  drivers/s390/crypto/ap_bus.c | 160 ++++++++++++++++++++++++++++++++---
>>  drivers/s390/crypto/ap_bus.h |   4 +
>>  2 files changed, 154 insertions(+), 10 deletions(-)
>>
> This doesn't touch the zcrypt drivers, so I _think_ the subject should
> rather be "s390/ap: driver callback to indicate resource in use". Harald?
That's right - but really not a big issue.
>
> Same for patch 13.