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Code Issues Releases Wiki Activity

vfio/ccw: Use the new device life cycle helpers

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ccw is the only exception which cannot use vfio_alloc_device() because
its private device structure is designed to serve both mdev and parent.
Life cycle of the parent is managed by css_driver so vfio_ccw_private
must be allocated/freed in css_driver probe/remove path instead of
conforming to vfio core life cycle for mdev.

Given that use a wait/completion scheme so the mdev remove path waits
after vfio_put_device() until receiving a completion notification from
@release. The completion indicates that all active references on
vfio_device have been released.

After that point although free of vfio_ccw_private is delayed to
css_driver it's at least guaranteed to have no parallel reference on
released vfio device part from other code paths.

memset() in @probe is removed. vfio_device is either already cleared
when probed for the first time or cleared in @release from last probe.

The right fix is to introduce separate structures for mdev and parent,
but this won't happen in short term per prior discussions.

Remove vfio_init/uninit_group_dev() as no user now.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Link: https://lore.kernel.org/r/20220921104401.38898-14-kevin.tian@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Kevin Tian 2022-09-21 18:43:59 +08:00 committed by Alex Williamson
parent ac1237912f
commit ebb72b765f
4 changed files with 53 additions and 28 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

52
drivers/s390/cio/vfio_ccw_ops.c
View file

@ -87,6 +87,15 @@ static struct attribute_group *mdev_type_groups[] = {
NULL,
};
static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev)
{
struct vfio_ccw_private *private =
container_of(vdev, struct vfio_ccw_private, vdev);
init_completion(&private->release_comp);
return 0;
}
static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
{
struct vfio_ccw_private *private = dev_get_drvdata(mdev->dev.parent);
@ -98,9 +107,9 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
if (atomic_dec_if_positive(&private->avail) < 0)
return -EPERM;
memset(&private->vdev, 0, sizeof(private->vdev));
vfio_init_group_dev(&private->vdev, &mdev->dev,
&vfio_ccw_dev_ops);
ret = vfio_init_device(&private->vdev, &mdev->dev, &vfio_ccw_dev_ops);
if (ret)
return ret;
VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: create\n",
private->sch->schid.cssid,
@ -109,16 +118,33 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
ret = vfio_register_emulated_iommu_dev(&private->vdev);
if (ret)
goto err_atomic;
goto err_put_vdev;
dev_set_drvdata(&mdev->dev, private);
return 0;
err_atomic:
vfio_uninit_group_dev(&private->vdev);
err_put_vdev:
vfio_put_device(&private->vdev);
atomic_inc(&private->avail);
return ret;
}
static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev)
{
struct vfio_ccw_private *private =
container_of(vdev, struct vfio_ccw_private, vdev);
/*
* We cannot free vfio_ccw_private here because it includes
* parent info which must be free'ed by css driver.
*
* Use a workaround by memset'ing the core device part and
* then notifying the remove path that all active references
* to this device have been released.
*/
memset(vdev, 0, sizeof(*vdev));
complete(&private->release_comp);
}
static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
{
struct vfio_ccw_private *private = dev_get_drvdata(mdev->dev.parent);
@ -130,7 +156,17 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
vfio_unregister_group_dev(&private->vdev);
vfio_uninit_group_dev(&private->vdev);
vfio_put_device(&private->vdev);
/*
* Wait for all active references on mdev are released so it
* is safe to defer kfree() to a later point.
*
* TODO: the clean fix is to split parent/mdev info from ccw
* private structure so each can be managed in its own life
* cycle.
*/
wait_for_completion(&private->release_comp);
atomic_inc(&private->avail);
}
@ -592,6 +628,8 @@ static void vfio_ccw_mdev_request(struct vfio_device *vdev, unsigned int count)
}
static const struct vfio_device_ops vfio_ccw_dev_ops = {
.init = vfio_ccw_mdev_init_dev,
.release = vfio_ccw_mdev_release_dev,
.open_device = vfio_ccw_mdev_open_device,
.close_device = vfio_ccw_mdev_close_device,
.read = vfio_ccw_mdev_read,

3
drivers/s390/cio/vfio_ccw_private.h
View file

@ -88,6 +88,7 @@ struct vfio_ccw_crw {
* @req_trigger: eventfd ctx for signaling userspace to return device
* @io_work: work for deferral process of I/O handling
* @crw_work: work for deferral process of CRW handling
* @release_comp: synchronization helper for vfio device release
*/
struct vfio_ccw_private {
struct vfio_device vdev;
@ -113,6 +114,8 @@ struct vfio_ccw_private {
struct eventfd_ctx *req_trigger;
struct work_struct io_work;
struct work_struct crw_work;
struct completion release_comp;
} __aligned(8);
int vfio_ccw_sch_quiesce(struct subchannel *sch);

23
drivers/vfio/vfio_main.c
View file

@ -483,28 +483,13 @@ static struct vfio_device *vfio_group_get_device(struct vfio_group *group,
/*
* VFIO driver API
*/
void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
const struct vfio_device_ops *ops)
{
init_completion(&device->comp);
device->dev = dev;
device->ops = ops;
}
EXPORT_SYMBOL_GPL(vfio_init_group_dev);
void vfio_uninit_group_dev(struct vfio_device *device)
{
vfio_release_device_set(device);
}
EXPORT_SYMBOL_GPL(vfio_uninit_group_dev);
/* Release helper called by vfio_put_device() */
void vfio_device_release(struct kref *kref)
{
struct vfio_device *device =
container_of(kref, struct vfio_device, kref);
vfio_uninit_group_dev(device);
vfio_release_device_set(device);
/*
* kvfree() cannot be done here due to a life cycle mess in
@ -562,7 +547,9 @@ int vfio_init_device(struct vfio_device *device, struct device *dev,
{
int ret;
vfio_init_group_dev(device, dev, ops);
init_completion(&device->comp);
device->dev = dev;
device->ops = ops;
if (ops->init) {
ret = ops->init(device);
@ -574,7 +561,7 @@ int vfio_init_device(struct vfio_device *device, struct device *dev,
return 0;
out_uninit:
vfio_uninit_group_dev(device);
vfio_release_device_set(device);
return ret;
}
EXPORT_SYMBOL_GPL(vfio_init_device);

3
include/linux/vfio.h
View file

@ -184,9 +184,6 @@ static inline void vfio_put_device(struct vfio_device *device)
kref_put(&device->kref, vfio_device_release);
}
void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
const struct vfio_device_ops *ops);
void vfio_uninit_group_dev(struct vfio_device *device);
int vfio_register_group_dev(struct vfio_device *device);
int vfio_register_emulated_iommu_dev(struct vfio_device *device);
void vfio_unregister_group_dev(struct vfio_device *device);