Re: [PATCH v12 14/17] s390/zcrypt: Notify driver on config changed and scan complete callbacks

From: Tony Krowiak
Date: Wed Dec 16 2020 - 15:55:22 EST



On 11/30/20 4:18 AM, h@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
On Tue, 24 Nov 2020 16:40:13 -0500
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
drivers/s390/crypto/ap_bus.c | 83 ++++++++++++++++++++++++++-
drivers/s390/crypto/ap_bus.h | 12 ++++
drivers/s390/crypto/vfio_ap_private.h | 14 ++++-
3 files changed, 106 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index 593573740981..3a63f6b33d8a 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -75,6 +75,7 @@ DEFINE_MUTEX(ap_perms_mutex);
EXPORT_SYMBOL(ap_perms_mutex);
static struct ap_config_info *ap_qci_info;
+static struct ap_config_info *ap_qci_info_old;
/*
* AP bus related debug feature things.
@@ -1440,6 +1441,52 @@ 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);
+}
+
+
+
/*
* Helper function for ap_scan_bus().
* Remove card device and associated queue devices.
@@ -1718,15 +1765,43 @@ static inline void ap_scan_adapter(int ap)
put_device(&ac->ap_dev.device);
}
+static int ap_get_configuration(void)
I believe this was Haralds request. I'm OO contaminated, but
the signature and the semantic does not mash well with my understanding
of a 'getter'. Especially the return value being actually a boolean and
'configuration changed/still the same'. From the signature it looks more
like the usual C-stlyle try to do something and return 0 if OK, otherwise
error code != 0.

I know where you're coming from as I spent 20 years as a C++
then a java programmer. The function does actually get the
latest host AP configuration and stores both the old and new
configurations, so in essence, the name is descriptive of
the function.


Since it's Haralds dominion, I'm not asking you to change this, but we
could at least document the return value (maybe also the behavior).

I will document the function in the next version.


+{
+ 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 ap;
+ int ap, config_changed = 0;
- ap_fetch_qci_info(ap_qci_info);
+ /* config change notify */
+ config_changed = ap_get_configuration();
+ if (config_changed)
+ notify_config_changed();
+ memcpy(ap_qci_info_old, ap_qci_info,
+ sizeof(struct ap_config_info));
Why is this memcpy needed? Isn't that already take care of in
ap_get_configuration()?

It is not needed and is actually an error since that copy is
already done in the ap_get_configuration() function.
Fortunately, it doesn't cause a problem since the vfio_ap
driver has already been notified of the configuration
change. Good catch, I'll remove this for the next version.


ap_select_domain();
AP_DBF_DBG("%s running\n", __func__);
@@ -1735,6 +1810,10 @@ static void ap_scan_bus(struct work_struct *unused)
for (ap = 0; ap <= ap_max_adapter_id; ap++)
ap_scan_adapter(ap);
+ /* scan complete notify */
+ if (config_changed)
+ notify_scan_complete();
+
/* 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 65edd847c65a..fbfbf6991718 100644
--- a/drivers/s390/crypto/ap_bus.h
+++ b/drivers/s390/crypto/ap_bus.h
@@ -146,6 +146,18 @@ struct ap_driver {
int (*probe)(struct ap_device *);
void (*remove)(struct ap_device *);
int (*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)
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 15b7cd74843b..7bd7e35eb2e0 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
These changes probably belong to some next patch...

With the things I just brought up clarified, you can slap a:
Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
over it next time.

@@ -36,14 +36,21 @@
* driver, be it using @mdev_list or writing the state of a
* single ap_matrix_mdev device. It's quite coarse but we don't
* expect much contention.
+ ** @ap_add: a bitmap specifying the APIDs added to the host AP configuration
+ * as notified by the AP bus via the on_cfg_chg callback.
+ * @aq_add: a bitmap specifying the APQIs added to the host AP configuration
+ * as notified by the AP bus via the on_cfg_chg callback.
*/
struct ap_matrix_dev {
struct device device;
atomic_t available_instances;
- struct ap_config_info info;
+ struct ap_config_info config_info;
+ struct ap_config_info config_info_prev;
struct list_head mdev_list;
struct mutex lock;
struct ap_driver *vfio_ap_drv;
+ DECLARE_BITMAP(ap_add, AP_DEVICES);
+ DECLARE_BITMAP(aq_add, AP_DEVICES);
};
extern struct ap_matrix_dev *matrix_dev;
@@ -90,6 +97,8 @@ struct ap_matrix_mdev {
struct kvm_s390_module_hook pqap_hook;
struct mdev_device *mdev;
DECLARE_HASHTABLE(qtable, 8);
+ DECLARE_BITMAP(ap_add, AP_DEVICES);
+ DECLARE_BITMAP(aq_add, AP_DEVICES);
};
extern int vfio_ap_mdev_register(void);
@@ -109,4 +118,7 @@ void vfio_ap_mdev_remove_queue(struct ap_device *queue);
int vfio_ap_mdev_resource_in_use(unsigned long *apm, unsigned long *aqm);
+void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
+ struct ap_config_info *old_config_info);
+
#endif /* _VFIO_AP_PRIVATE_H_ */