[Qemu-devel] [PATCH RFC v3 10/15] vfio: ccw: realize VFIO_DEVICE_RESET ioctl

[Dong Jia Shi]

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 <address@hidden>
---
 drivers/s390/cio/vfio_ccw_ops.c | 47 +++++++++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 14 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index f3300dd..125818c 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;
        }
-- 
2.8.4