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>

1 files changed, 33 insertions, 14 deletions

diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index f3300ddded3f..125818cdf305 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/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;
         }