Re: [PATCH v10 12/16] s390/zcrypt: Notify driver on config changed and scan complete callbacks

Halil Pasic
2020-09-27T01:39:55Z

On Fri, 21 Aug 2020 15:56:12 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> This patch intruduces an extension to the ap bus to notify drivers
> on crypto config changed and bus scan complete events.
> Two new callbacks are introduced for ap_drivers:
>
> void (*on_config_changed)(struct ap_config_info *new_config_info,
> struct ap_config_info *old_config_info);
> void (*on_scan_complete)(struct ap_config_info *new_config_info,
> struct ap_config_info *old_config_info);
>
> Both callbacks are optional. Both callbacks are only triggered
> when QCI information is available (facility bit 12):
>
> * The on_config_changed 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 or 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 in bulk rather than one at a time as its remove
> callback is invoked. It will also allow the device driver to do any
> any cleanup prior to giving control back to the bus piecemeal. This is
> particularly important for the vfio_ap driver because there may be
> guests using the queues at the time.
>
> * 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 or domains have
> been added to the host's configuration, it will create new devices in
> the AP bus subsystem's device model. This callback also allows the driver
> to process all of the new devices in bulk.
>
> 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>
> ---
> drivers/s390/crypto/ap_bus.c | 85 +++++++++++++++++++++++++++++++++++-
> drivers/s390/crypto/ap_bus.h | 12 +++++
> 2 files changed, 96 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
> index db27bd931308..cbf4c4d2e573 100644
> --- a/drivers/s390/crypto/ap_bus.c
> +++ b/drivers/s390/crypto/ap_bus.c
> @@ -73,8 +73,10 @@ struct ap_perms ap_perms;
> EXPORT_SYMBOL(ap_perms);
> DEFINE_MUTEX(ap_perms_mutex);
> EXPORT_SYMBOL(ap_perms_mutex);
> +DEFINE_MUTEX(ap_config_lock);
>
> static struct ap_config_info *ap_qci_info;
> +static struct ap_config_info *ap_qci_info_old;
>
> /*
> * AP bus related debug feature things.
> @@ -1412,6 +1414,52 @@ static int __match_queue_device_with_queue_id(struct device *dev, const void *da
> && AP_QID_QUEUE(to_ap_queue(dev)->qid) == (int)(long) data;
> }
>
> +/* Helper function for notify_config_changed */
> +static int __drv_notify_config_changed(struct device_driver *drv, void *data)
> +{
> + struct ap_driver *ap_drv = to_ap_drv(drv);
> +
> + if (try_module_get(drv->owner)) {
> + if (ap_drv->on_config_changed)
> + ap_drv->on_config_changed(ap_qci_info,
> + ap_qci_info_old);
> + module_put(drv->owner);
> + }
> +
> + return 0;
> +}
> +
> +/* Notify all drivers about an qci config change */
> +static inline void notify_config_changed(void)
> +{
> + bus_for_each_drv(&ap_bus_type, NULL, NULL,
> + __drv_notify_config_changed);
> +}
> +
> +/* Helper function for notify_scan_complete */
> +static int __drv_notify_scan_complete(struct device_driver *drv, void *data)
> +{
> + struct ap_driver *ap_drv = to_ap_drv(drv);
> +
> + if (try_module_get(drv->owner)) {
> + if (ap_drv->on_scan_complete)
> + ap_drv->on_scan_complete(ap_qci_info,
> + ap_qci_info_old);
> + module_put(drv->owner);
> + }
> +
> + return 0;
> +}
> +
> +/* Notify all drivers about bus scan complete */
> +static inline void notify_scan_complete(void)
> +{
> + bus_for_each_drv(&ap_bus_type, NULL, NULL,
> + __drv_notify_scan_complete);
> +}
> +
> +
> +

Too many blank lines?

> /*
> * Helper function for ap_scan_bus().
> * Does the scan bus job for the given adapter id.
> @@ -1565,15 +1613,44 @@ static void _ap_scan_bus_adapter(int id)
> put_device(&ac->ap_dev.device);
> }
>
> +static int ap_config_changed(void)
> +{
> + int cfg_chg = 0;
> +
> + if (ap_qci_info) {
> + if (!ap_qci_info_old) {
> + ap_qci_info_old = kzalloc(sizeof(*ap_qci_info_old),
> + GFP_KERNEL);
> + if (!ap_qci_info_old)
> + return 0;
> + } else {
> + memcpy(ap_qci_info_old, ap_qci_info,
> + sizeof(struct ap_config_info));
> + }
> + ap_fetch_qci_info(ap_qci_info);
> + cfg_chg = memcmp(ap_qci_info,
> + ap_qci_info_old,
> + sizeof(struct ap_config_info)) != 0;
> + }
> +
> + return cfg_chg;
> +}
> +
> /**
> * ap_scan_bus(): Scan the AP bus for new devices
> * Runs periodically, workqueue timer (ap_config_time)
> */
> static void ap_scan_bus(struct work_struct *unused)
> {
> - int id;
> + int id, config_changed = 0;
>
> ap_fetch_qci_info(ap_qci_info);

Do we still need this ap_fetch_qci_info()? ...

> + mutex_lock(&ap_config_lock);

The usage of ap_qci_info does not seem to change substantially, and
ap_qci_info_old is not used unlike. I believe if we need ap_config_lock
now, then we used to need it before. And then adding this lock should
really be a separate patch than clearly advertises its fix nature.

> +
> + /* config change notify */
> + config_changed = ap_config_changed();

... I mean ap_config_changed() does a ap_fetch_qci_info()
of it's own.

Otherwise looks OK!

Regards,
Halil

> + if (config_changed)
> + notify_config_changed();
> ap_select_domain();
>
> AP_DBF(DBF_DEBUG, "%s running\n", __func__);
> @@ -1582,6 +1659,12 @@ static void ap_scan_bus(struct work_struct *unused)
> for (id = 0; id < AP_DEVICES; id++)
> _ap_scan_bus_adapter(id);
>
> + /* scan complete notify */
> + if (config_changed)
> + notify_scan_complete();
> +
> + mutex_unlock(&ap_config_lock);
> +
> /* check if there is at least one queue available with default domain */
> if (ap_domain_index >= 0) {
> struct device *dev =
> diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
> index 48c57b3d53a0..3fc743ac549c 100644
> --- a/drivers/s390/crypto/ap_bus.h
> +++ b/drivers/s390/crypto/ap_bus.h
> @@ -137,6 +137,18 @@ struct ap_driver {
> int (*probe)(struct ap_device *);
> void (*remove)(struct ap_device *);
> bool (*in_use)(unsigned long *apm, unsigned long *aqm);
> + /*
> + * Called at the start of the ap bus scan function when
> + * the crypto config information (qci) has changed.
> + */
> + void (*on_config_changed)(struct ap_config_info *new_config_info,
> + struct ap_config_info *old_config_info);
> + /*
> + * Called at the end of the ap bus scan function when
> + * the crypto config information (qci) has changed.
> + */
> + void (*on_scan_complete)(struct ap_config_info *new_config_info,
> + struct ap_config_info *old_config_info);
> };
>
> #define to_ap_drv(x) container_of((x), struct ap_driver, driver)