Re: [PATCH v18 15/18] s390/vfio-ap: handle config changed and scan complete notification

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On 2/14/22 19:50, Tony Krowiak wrote:
...
@@ -790,13 +788,17 @@ static void vfio_ap_unlink_apqn_fr_mdev(struct ap_matrix_mdev *matrix_mdev,
q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
  	/* If the queue is assigned to the matrix mdev, unlink it. */
-	if (q)
+	if (q) {
  		vfio_ap_unlink_queue_fr_mdev(q);
- /* If the queue is assigned to the APCB, store it in @qtable. */
-	if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
-	    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
-		hash_add(qtable->queues, &q->mdev_qnode, q->apqn);
+		/* If the queue is assigned to the APCB, store it in @qtable. */
+		if (qtable) {
+			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
+			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
+				hash_add(qtable->queues, &q->mdev_qnode,
+					 q->apqn);
+		}
+	}
  }

This appears to be an unrelated change. Does this belong in this patch?


  /**
@@ -1271,7 +1273,7 @@ static const struct attribute_group *vfio_ap_mdev_attr_groups[] = {
   * @matrix_mdev: a mediated matrix device
   * @kvm: reference to KVM instance
   *
- * Note: The matrix_dev->lock must be taken prior to calling
+ * Note: The matrix_dev->mdevs_lock must be taken prior to calling

This also seems to be unrelated.


   * this function; however, the lock will be temporarily released while the
   * guest's AP configuration is set to avoid a potential lockdep splat.
   * The kvm->lock is taken to set the guest's AP configuration which, under
@@ -1355,7 +1357,7 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
   * @matrix_mdev: a matrix mediated device
   * @kvm: the pointer to the kvm structure being unset.
   *
- * Note: The matrix_dev->lock must be taken prior to calling
+ * Note: The matrix_dev->mdevs_lock must be taken prior to calling

Same here.

   * this function; however, the lock will be temporarily released while the
   * guest's AP configuration is cleared to avoid a potential lockdep splat.
   * The kvm->lock is taken to clear the guest's AP configuration which, under
@@ -1708,6 +1710,27 @@ static void vfio_ap_mdev_put_qlocks(struct ap_matrix_mdev *matrix_mdev)
  	mutex_unlock(&matrix_dev->guests_lock);
  }
+static bool vfio_ap_mdev_do_filter_matrix(struct ap_matrix_mdev *matrix_mdev,
+					  struct vfio_ap_queue *q)
+{
+	unsigned long apid = AP_QID_CARD(q->apqn);
+	unsigned long apqi = AP_QID_QUEUE(q->apqn);
+
+	/*
+	 * If the queue is being probed because its APID or APQI is in the
+	 * process of being added to the host's AP configuration, then we don't
+	 * want to filter the matrix now as the filtering will be done after
+	 * the driver is notified that the AP bus scan operation has completed
+	 * (see the vfio_ap_on_scan_complete callback function).
+	 */
+	if (test_bit_inv(apid, matrix_mdev->apm_add) ||
+	    test_bit_inv(apqi, matrix_mdev->aqm_add))
+		return false;
+
+
+	return true;
+}
+
  int vfio_ap_mdev_probe_queue(struct ap_device *apdev)
  {
  	struct vfio_ap_queue *q;
@@ -1725,10 +1748,15 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev)
  		vfio_ap_mdev_link_queue(matrix_mdev, q);
  		memset(apm, 0, sizeof(apm));
  		set_bit_inv(AP_QID_CARD(q->apqn), apm);
-		if (vfio_ap_mdev_filter_matrix(apm, q->matrix_mdev->matrix.aqm,
-					       q->matrix_mdev))
-			vfio_ap_mdev_hotplug_apcb(q->matrix_mdev);
+
+		if (vfio_ap_mdev_do_filter_matrix(q->matrix_mdev, q)) {
+			if (vfio_ap_mdev_filter_matrix(apm,
+						q->matrix_mdev->matrix.aqm,
+						q->matrix_mdev))
+				vfio_ap_mdev_hotplug_apcb(q->matrix_mdev);
+		}
  	}
+
  	dev_set_drvdata(&apdev->device, q);
  	vfio_ap_mdev_put_qlocks(matrix_mdev);
@@ -1783,10 +1811,15 @@ void vfio_ap_mdev_remove_queue(struct ap_device *apdev) apid = AP_QID_CARD(q->apqn);
  		apqi = AP_QID_QUEUE(q->apqn);
-		if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
-		    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm)) {
-			clear_bit_inv(apid, matrix_mdev->shadow_apcb.apm);
-			vfio_ap_mdev_hotplug_apcb(matrix_mdev);
+
+		/*
+		 * If the queue is assigned to the guest's APCB, then remove
+		 * the adapter's APID from the APCB and hot it into the guest.
+		 */
+		if (test_bit_inv(apid, q->matrix_mdev->shadow_apcb.apm) &&
+		    test_bit_inv(apqi, q->matrix_mdev->shadow_apcb.aqm)) {
+			clear_bit_inv(apid, q->matrix_mdev->shadow_apcb.apm);
+			vfio_ap_mdev_hotplug_apcb(q->matrix_mdev);

It looks like this a bug fix unrelated to this patch...?

@@ -1842,3 +1875,267 @@ int vfio_ap_mdev_resource_in_use(unsigned long *apm, unsigned long *aqm) return ret;
  }
+
+/**
+ * vfio_ap_mdev_hot_unplug_cfg - hot unplug the adapters, domains and control
+ *				 domains that have been removed from the host's
+ *				 AP configuration from a guest.
+ *
+ * @guest: the guest
+ * @aprem: the adapters that have been removed from the host's AP configuration
+ * @aqrem: the domains that have been removed from the host's AP configuration
+ * @cdrem: the control domains that have been removed from the host's AP
+ *	   configuration.
+ */
+static void vfio_ap_mdev_hot_unplug_cfg(struct ap_matrix_mdev *matrix_mdev,
+					unsigned long *aprem,
+					unsigned long *aqrem,
+					unsigned long *cdrem)
+{
+	bool do_hotplug = false;

__bitmap_andnot() returns an int, so I think you should use an int here.


+	if (!bitmap_empty(aprem, AP_DEVICES)) {
+		do_hotplug |= bitmap_andnot(matrix_mdev->shadow_apcb.apm,
+					    matrix_mdev->shadow_apcb.apm,
+					    aprem, AP_DEVICES);

Also, replace the |= with an = here. This is the first assignment so no
need to do a logical OR as there is no pre-existing data to preserve.


+	}
+
+	if (!bitmap_empty(aqrem, AP_DOMAINS)) {
+		do_hotplug |= bitmap_andnot(matrix_mdev->shadow_apcb.aqm,
+					    matrix_mdev->shadow_apcb.aqm,
+					    aqrem, AP_DEVICES);
+	}
+
+	if (!bitmap_empty(cdrem, AP_DOMAINS))
+		do_hotplug |= bitmap_andnot(matrix_mdev->shadow_apcb.adm,
+					    matrix_mdev->shadow_apcb.adm,
+					    cdrem, AP_DOMAINS);
+
+	if (do_hotplug)
+		vfio_ap_mdev_hotplug_apcb(matrix_mdev);
+}
+
+/**
+ * vfio_ap_mdev_cfg_remove - determines which guests are using the adapters,
+ *			     domains and control domains that have been removed
+ *			     from the host AP configuration and unplugs them
+ *			     from those guests.
+ *
+ * @ap_remove:	bitmap specifying which adapters have been removed from the host
+ *		config.
+ * @aq_remove:	bitmap specifying which domains have been removed from the host
+ *		config.
+ * @cd_remove:	bitmap specifying which control domains have been removed from
+ *		the host config.
+ */
...
+/**
+ * vfio_ap_mdev_on_cfg_remove - responds to the removal of adapters, domains and
+ *				control domains from the host AP configuration
+ *				by unplugging them from the guests that are
+ *				using them.
+ */
+static void vfio_ap_mdev_on_cfg_remove(void)
+{
+	int ap_remove, aq_remove, cd_remove;

These can all be replaced with a single variable, just like you did with do_add.

+	DECLARE_BITMAP(aprem, AP_DEVICES);
+	DECLARE_BITMAP(aqrem, AP_DOMAINS);
+	DECLARE_BITMAP(cdrem, AP_DOMAINS);
+	unsigned long *cur_apm, *cur_aqm, *cur_adm;
+	unsigned long *prev_apm, *prev_aqm, *prev_adm;
+
+	cur_apm = (unsigned long *)matrix_dev->config_info.apm;
+	cur_aqm = (unsigned long *)matrix_dev->config_info.aqm;
+	cur_adm = (unsigned long *)matrix_dev->config_info.adm;
+	prev_apm = (unsigned long *)matrix_dev->config_info_prev.apm;
+	prev_aqm = (unsigned long *)matrix_dev->config_info_prev.aqm;
+	prev_adm = (unsigned long *)matrix_dev->config_info_prev.adm;
+
+	ap_remove = bitmap_andnot(aprem, prev_apm, cur_apm, AP_DEVICES);
+	aq_remove = bitmap_andnot(aqrem, prev_aqm, cur_aqm, AP_DOMAINS);
+	cd_remove = bitmap_andnot(cdrem, prev_adm, cur_adm, AP_DOMAINS);
+
+	if (ap_remove || aq_remove || cd_remove)
+		vfio_ap_mdev_cfg_remove(aprem, aqrem, cdrem);
+}
...
+/**
+ * vfio_ap_on_cfg_changed - handles notification of changes to the host AP
+ *			    configuration.
+ *
+ * @new_config_info: the new host AP configuration
+ * @old_config_info: the previous host AP configuration
+ */
+void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
+			    struct ap_config_info *old_config_info)
+{
+	mutex_lock(&matrix_dev->guests_lock);
+
+	memcpy(&matrix_dev->config_info_prev, old_config_info,
+		       sizeof(struct ap_config_info));
+	memcpy(&matrix_dev->config_info, new_config_info,
+	       sizeof(struct ap_config_info));

Why are we storing old_config_info in the matrix_dev? It appears to only
be used within the functions called from right here. Why not just pass it
as an argument?

+	vfio_ap_mdev_on_cfg_remove();
+	vfio_ap_mdev_on_cfg_add();
+
+	mutex_unlock(&matrix_dev->guests_lock);
+}

Here is an idea to restructure things... consider combining logic from
vfio_ap_mdev_on_cfg_remove and vfio_ap_mdev_on_cfg_add with
vfio_ap_on_cfg_changed. This makes vfio_ap_on_cfg_changed() longer but
it eliminates some duplicated code and gets rid of both
vfio_ap_mdev_on_cfg_remove and vfio_ap_mdev_on_cfg_add.
note: Untested... :)

void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
			    struct ap_config_info *old_config_info)
{
	DECLARE_BITMAP(changed_adapters, AP_DEVICES);
	DECLARE_BITMAP(changed_domains, AP_DOMAINS);
	DECLARE_BITMAP(changed_cdoms, AP_DOMAINS);
	unsigned long *cur_apm, *cur_aqm, *cur_adm;
	unsigned long *prev_apm, *prev_aqm, *prev_adm;

	cur_apm = (unsigned long *)new_config_info->apm;
	cur_aqm = (unsigned long *)new_config_info->aqm;
	cur_adm = (unsigned long *)new_config_info->adm;
	prev_apm = (unsigned long *)old_config_info->apm;
	prev_aqm = (unsigned long *)old_config_info->.aqm;
	prev_adm = (unsigned long *)old_config_info->adm;

	mutex_lock(&matrix_dev->guests_lock);
	
	/* Handle host configuration removals */
	bitmap_andnot(changed_adapters, prev_apm, cur_apm, AP_DEVICES);
	bitmap_andnot(changed_domains, prev_aqm, cur_aqm, AP_DOMAINS);
	bitmap_andnot(changed_cdoms, prev_adm, cur_adm, AP_DOMAINS);

	if (changed_adapters || changed_domains || changed_cdoms)
		vfio_ap_mdev_cfg_remove(aprem, aqrem, cdrem);

	bitmap_clear(changed_adapters, 0, AP_DEVICES);
	bitmap_clear(changed_domains, 0, AP_DOMAINS);
	bitmap_clear(changed_cdoms, 0, AP_DOMAINS);

	/* Handle host configuration additions */
	bitmap_andnot(changed_adapters, cur_apm, prev_apm, AP_DEVICES);
	bitmap_andnot(changed_domains, cur_aqm, prev_aqm, AP_DOMAINS);
	bitmap_andnot(changed_cdoms, cur_adm, prev_adm, AP_DOMAINS);

	if (changed_adapters || changed_domains || changed_cdoms) {
		vfio_ap_mdev_cfg_add(apm_add, aqm_add, adm_add);
	}
	mutex_unlock(&matrix_dev->guests_lock);
}

Not sure if where I put the locking is 100% correct. We could do a
lock/unlock around each call to vfio_ap_mdev_cfg_{remove|add} but
there is probablyt no point to that, right?

Also, a side effect of these changes is that matrix_dev->config_info
is no longer updated. I guess we either would need to update it here
or update it wherever it was originally updated before this patrch.

--
-- Jason J. Herne (jjherne@xxxxxxxxxxxxx)



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