linux-kernel - Re: [PATCH v13 12/15] s390/zcrypt: Notify driver on config changed and scan complete callbacks

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Date:   Tue, 12 Jan 2021 17:58:50 +0100
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, mjrosato@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v13 12/15] s390/zcrypt: Notify driver on config changed
 and scan complete callbacks

On Tue, 22 Dec 2020 20:16:03 -0500
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> This patch intruduces an extension to the ap bus to notify device drivers
> when the host AP configuration changes - i.e., adapters, domains or
> control domains are added or removed. To that end, two new callbacks are
> introduced for AP device drivers:
> 
>   void (*on_config_changed)(struct ap_config_info *new_config_info,
>                             struct ap_config_info *old_config_info);
> 
>      This callback is invoked at the start of the AP bus scan
>      function when it determines that the host AP configuration information
>      has changed since the previous scan. This is done by storing
>      an old and current QCI info struct and comparing them. If there is any
>      difference, the callback is invoked.
> 
>      Note that when the AP bus scan detects that AP adapters, domains or
>      control domains have been removed from the host's AP configuration, it
>      will remove the associated devices from the AP bus subsystem's device
>      model. This callback gives the device driver a chance to respond to
>      the removal of the AP devices from the host configuration prior to
>      calling the device driver's remove callback. The primary purpose of
>      this callback is to allow the vfio_ap driver to do a bulk unplug of
>      all affected adapters, domains and control domains from affected
>      guests rather than unplugging them one at a time when the remove
>      callback is invoked.
> 
>   void (*on_scan_complete)(struct ap_config_info *new_config_info,
>                            struct ap_config_info *old_config_info);
> 
>      The on_scan_complete callback is invoked after the ap bus scan is
>      complete if the host AP configuration data has changed.
> 
>      Note that when the AP bus scan detects that adapters, domains or
>      control domains have been added to the host's configuration, it will
>      create new devices in the AP bus subsystem's device model. The primary
>      purpose of this callback is to allow the vfio_ap driver to do a bulk
>      plug of all affected adapters, domains and control domains into
>      affected guests rather than plugging them one at a time when the
>      probe callback is invoked.
> 
> Please note that changes to the apmask and aqmask do not trigger
> these two callbacks since the bus scan function is not invoked by changes
> to those masks.
> 
> Signed-off-by: Harald Freudenberger <freude@...ux.ibm.com>
> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>

Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>

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