vfio: ccw: realize VFIO_DEVICE_RESET ioctl

Introduce VFIO_DEVICE_RESET ioctl for vfio-ccw to make it possible
to hot-reset the device.

We try to achieve a reset by first disabling the subchannel and
then enabling it again: this should clear all state at the subchannel.
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-Id: <20170317031743.40128-11-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

drivers/s390/cio/vfio_ccw_ops.c

@@ -12,6 +12,32 @@
 
 #include "vfio_ccw_private.h"
 
+static int vfio_ccw_mdev_reset(struct mdev_device *mdev)
+{
+	struct vfio_ccw_private *private;
+	struct subchannel *sch;
+	int ret;
+
+	private = dev_get_drvdata(mdev_parent_dev(mdev));
+	if (!private)
+		return -ENODEV;
+
+	sch = private->sch;
+	/*
+	 * TODO:
+	 * In the cureent stage, some things like "no I/O running" and "no
+	 * interrupt pending" are clear, but we are not sure what other state
+	 * we need to care about.
+	 * There are still a lot more instructions need to be handled. We
+	 * should come back here later.
+	 */
+	ret = vfio_ccw_sch_quiesce(sch);
+	if (ret)
+		return ret;
+
+	return cio_enable_subchannel(sch, (u32)(unsigned long)sch);
+}
+
 static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
 				  unsigned long action,
 				  void *data)
@@ -28,15 +54,11 @@ static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
 	 */
 	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
 		struct vfio_iommu_type1_dma_unmap *unmap = data;
-		struct subchannel *sch = private->sch;
 
 		if (!cp_iova_pinned(&private->cp, unmap->iova))
 			return NOTIFY_OK;
 
-		if (vfio_ccw_sch_quiesce(sch))
-			return NOTIFY_BAD;
-
-		if (cio_enable_subchannel(sch, (u32)(unsigned long)sch))
+		if (vfio_ccw_mdev_reset(private->mdev))
 			return NOTIFY_BAD;
 
 		cp_free(&private->cp);
@@ -100,16 +122,11 @@ static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 
 static int vfio_ccw_mdev_remove(struct mdev_device *mdev)
 {
-	struct vfio_ccw_private *private;
-	struct subchannel *sch;
+	struct vfio_ccw_private *private =
+		dev_get_drvdata(mdev_parent_dev(mdev));
 	int ret;
 
-	private = dev_get_drvdata(mdev_parent_dev(mdev));
-	sch = private->sch;
-	ret = vfio_ccw_sch_quiesce(sch);
-	if (ret)
-		return ret;
-	ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch);
+	ret = vfio_ccw_mdev_reset(mdev);
 	if (ret)
 		return ret;
 
@@ -190,7 +207,7 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
 
 static int vfio_ccw_mdev_get_device_info(struct vfio_device_info *info)
 {
-	info->flags = VFIO_DEVICE_FLAGS_CCW;
+	info->flags = VFIO_DEVICE_FLAGS_CCW | VFIO_DEVICE_FLAGS_RESET;
 	info->num_regions = VFIO_CCW_NUM_REGIONS;
 	info->num_irqs = 0;
 
@@ -260,6 +277,8 @@ static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device *mdev,
 
 		return copy_to_user((void __user *)arg, &info, minsz);
 	}
+	case VFIO_DEVICE_RESET:
+		return vfio_ccw_mdev_reset(mdev);
 	default:
 		return -ENOTTY;
 	}