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 [off-list ref] 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@linux.ibm.com>
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>

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

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