[RFC PATCH v2 1/2] s390/vfio-ap: Signal eventfd when guest AP configuration is changed

[Rorie Reyes <rreyes@linux.ibm.com>]

In this patch, an eventfd object is created by the vfio_ap device driver
and used to notify userspace when a guests's AP configuration is
dynamically changed. Such changes may occur whenever:

* An adapter, domain or control domain is assigned to or unassigned from a
  mediated device that is attached to the guest.
* A queue assigned to the mediated device that is attached to a guest is
  bound to or unbound from the vfio_ap device driver. This can occur
  either by manually binding/unbinding the queue via the vfio_ap driver's
  sysfs bind/unbind attribute interfaces, or because an adapter, domain or
  control domain assigned to the mediated device is added to or removed
  from the host's AP configuration via an SE/HMC

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
Reviewed-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 52 ++++++++++++++++++++++++++-
 drivers/s390/crypto/vfio_ap_private.h |  2 ++
 include/uapi/linux/vfio.h             |  1 +
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index a52c2690933f..c6ff4ab13f16 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -650,13 +650,22 @@ static void vfio_ap_matrix_init(struct ap_config_info *info,
 	matrix->adm_max = info->apxa ? info->nd : 15;
 }
 
+static void signal_guest_ap_cfg_changed(struct ap_matrix_mdev *matrix_mdev)
+{
+		if (matrix_mdev->cfg_chg_trigger)
+			eventfd_signal(matrix_mdev->cfg_chg_trigger);
+}
+
 static void vfio_ap_mdev_update_guest_apcb(struct ap_matrix_mdev *matrix_mdev)
 {
-	if (matrix_mdev->kvm)
+	if (matrix_mdev->kvm) {
 		kvm_arch_crypto_set_masks(matrix_mdev->kvm,
 					  matrix_mdev->shadow_apcb.apm,
 					  matrix_mdev->shadow_apcb.aqm,
 					  matrix_mdev->shadow_apcb.adm);
+
+		signal_guest_ap_cfg_changed(matrix_mdev);
+	}
 }
 
 static bool vfio_ap_mdev_filter_cdoms(struct ap_matrix_mdev *matrix_mdev)
@@ -792,6 +801,7 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 	if (ret)
 		goto err_put_vdev;
 	matrix_mdev->req_trigger = NULL;
+	matrix_mdev->cfg_chg_trigger = NULL;
 	dev_set_drvdata(&mdev->dev, matrix_mdev);
 	mutex_lock(&matrix_dev->mdevs_lock);
 	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
@@ -1860,6 +1870,7 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
 		get_update_locks_for_kvm(kvm);
 
 		kvm_arch_crypto_clear_masks(kvm);
+		signal_guest_ap_cfg_changed(matrix_mdev);
 		vfio_ap_mdev_reset_queues(matrix_mdev);
 		kvm_put_kvm(kvm);
 		matrix_mdev->kvm = NULL;
@@ -2097,6 +2108,10 @@ static ssize_t vfio_ap_get_irq_info(unsigned long arg)
 		info.count = 1;
 		info.flags = VFIO_IRQ_INFO_EVENTFD;
 		break;
+	case VFIO_AP_CFG_CHG_IRQ_INDEX:
+		info.count = 1;
+		info.flags = VFIO_IRQ_INFO_EVENTFD;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -2160,6 +2175,39 @@ static int vfio_ap_set_request_irq(struct ap_matrix_mdev *matrix_mdev,
 	return 0;
 }
 
+static int vfio_ap_set_cfg_change_irq(struct ap_matrix_mdev *matrix_mdev, unsigned long arg)
+{
+	s32 fd;
+	void __user *data;
+	unsigned long minsz;
+	struct eventfd_ctx *cfg_chg_trigger;
+
+	minsz = offsetofend(struct vfio_irq_set, count);
+	data = (void __user *)(arg + minsz);
+
+	if (get_user(fd, (s32 __user *)data))
+		return -EFAULT;
+
+	if (fd == -1) {
+		if (matrix_mdev->cfg_chg_trigger)
+			eventfd_ctx_put(matrix_mdev->cfg_chg_trigger);
+		matrix_mdev->cfg_chg_trigger = NULL;
+	} else if (fd >= 0) {
+		cfg_chg_trigger = eventfd_ctx_fdget(fd);
+		if (IS_ERR(cfg_chg_trigger))
+			return PTR_ERR(cfg_chg_trigger);
+
+		if (matrix_mdev->cfg_chg_trigger)
+			eventfd_ctx_put(matrix_mdev->cfg_chg_trigger);
+
+		matrix_mdev->cfg_chg_trigger = cfg_chg_trigger;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int vfio_ap_set_irqs(struct ap_matrix_mdev *matrix_mdev,
 			    unsigned long arg)
 {
@@ -2175,6 +2223,8 @@ static int vfio_ap_set_irqs(struct ap_matrix_mdev *matrix_mdev,
 		switch (irq_set.index) {
 		case VFIO_AP_REQ_IRQ_INDEX:
 			return vfio_ap_set_request_irq(matrix_mdev, arg);
+		case VFIO_AP_CFG_CHG_IRQ_INDEX:
+			return vfio_ap_set_cfg_change_irq(matrix_mdev, arg);
 		default:
 			return -EINVAL;
 		}
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 437a161c8659..37de9c69b6eb 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -105,6 +105,7 @@ struct ap_queue_table {
  * @mdev:	the mediated device
  * @qtable:	table of queues (struct vfio_ap_queue) assigned to the mdev
  * @req_trigger eventfd ctx for signaling userspace to return a device
+ * @cfg_chg_trigger eventfd ctx to signal AP config changed to userspace
  * @apm_add:	bitmap of APIDs added to the host's AP configuration
  * @aqm_add:	bitmap of APQIs added to the host's AP configuration
  * @adm_add:	bitmap of control domain numbers added to the host's AP
@@ -120,6 +121,7 @@ struct ap_matrix_mdev {
 	struct mdev_device *mdev;
 	struct ap_queue_table qtable;
 	struct eventfd_ctx *req_trigger;
+	struct eventfd_ctx *cfg_chg_trigger;
 	DECLARE_BITMAP(apm_add, AP_DEVICES);
 	DECLARE_BITMAP(aqm_add, AP_DOMAINS);
 	DECLARE_BITMAP(adm_add, AP_DOMAINS);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index c8dbf8219c4f..a2d3e1ac6239 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -671,6 +671,7 @@ enum {
  */
 enum {
 	VFIO_AP_REQ_IRQ_INDEX,
+	VFIO_AP_CFG_CHG_IRQ_INDEX,
 	VFIO_AP_NUM_IRQS
 };
 
-- 
2.39.5 (Apple Git-154)