[PATCH 5.10 391/545] vfio: Split creation of a vfio_device into init and register ops

Greg Kroah-Hartman
2022-08-19T16:34:26Z

From: Jason Gunthorpe <jgg@nvidia.com>

[ Upstream commit 0bfc6a4ea63c2adac71a824397ef48f28dbc5e47 ]

This makes the struct vfio_device part of the public interface so it
can be used with container_of and so forth, as is typical for a Linux
subystem.

This is the first step to bring some type-safety to the vfio interface by
allowing the replacement of 'void *' and 'struct device *' inputs with a
simple and clear 'struct vfio_device *'

For now the self-allocating vfio_add_group_dev() interface is kept so each
user can be updated as a separate patch.

The expected usage pattern is

driver core probe() function:
my_device = kzalloc(sizeof(*mydevice));
vfio_init_group_dev(&my_device->vdev, dev, ops, mydevice);
/* other driver specific prep */
vfio_register_group_dev(&my_device->vdev);
dev_set_drvdata(dev, my_device);

driver core remove() function:
my_device = dev_get_drvdata(dev);
vfio_unregister_group_dev(&my_device->vdev);
/* other driver specific tear down */
kfree(my_device);

Allowing the driver to be able to use the drvdata and vfio_device to go
to/from its own data.

The pattern also makes it clear that vfio_register_group_dev() must be
last in the sequence, as once it is called the core code can immediately
start calling ops. The init/register gap is provided to allow for the
driver to do setup before ops can be called and thus avoid races.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Liu Yi L <yi.l.liu@intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Message-Id: <3-v3-225de1400dfc+4e074-vfio1_jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Documentation/driver-api/vfio.rst | 31 ++++----
drivers/vfio/vfio.c | 125 ++++++++++++++++--------------
include/linux/vfio.h | 16 ++++
3 files changed, 99 insertions(+), 73 deletions(-)

diff --git a/Documentation/driver-api/vfio.rst b/Documentation/driver-api/vfio.rst
index f1a4d3c3ba0b..d3a02300913a 100644
--- a/Documentation/driver-api/vfio.rst
+++ b/Documentation/driver-api/vfio.rst
@@ -249,18 +249,23 @@ VFIO bus driver API

VFIO bus drivers, such as vfio-pci make use of only a few interfaces
into VFIO core. When devices are bound and unbound to the driver,
-the driver should call vfio_add_group_dev() and vfio_del_group_dev()
-respectively::
-
- extern int vfio_add_group_dev(struct device *dev,
- const struct vfio_device_ops *ops,
- void *device_data);
-
- extern void *vfio_del_group_dev(struct device *dev);
-
-vfio_add_group_dev() indicates to the core to begin tracking the
-iommu_group of the specified dev and register the dev as owned by
-a VFIO bus driver. The driver provides an ops structure for callbacks
+the driver should call vfio_register_group_dev() and
+vfio_unregister_group_dev() respectively::
+
+ void vfio_init_group_dev(struct vfio_device *device,
+ struct device *dev,
+ const struct vfio_device_ops *ops,
+ void *device_data);
+ int vfio_register_group_dev(struct vfio_device *device);
+ void vfio_unregister_group_dev(struct vfio_device *device);
+
+The driver should embed the vfio_device in its own structure and call
+vfio_init_group_dev() to pre-configure it before going to registration.
+vfio_register_group_dev() indicates to the core to begin tracking the
+iommu_group of the specified dev and register the dev as owned by a VFIO bus
+driver. Once vfio_register_group_dev() returns it is possible for userspace to
+start accessing the driver, thus the driver should ensure it is completely
+ready before calling it. The driver provides an ops structure for callbacks
similar to a file operations structure::

struct vfio_device_ops {
@@ -276,7 +281,7 @@ similar to a file operations structure::
};

Each function is passed the device_data that was originally registered
-in the vfio_add_group_dev() call above. This allows the bus driver
+in the vfio_register_group_dev() call above. This allows the bus driver
an easy place to store its opaque, private data. The open/release
callbacks are issued when a new file descriptor is created for a
device (via VFIO_GROUP_GET_DEVICE_FD). The ioctl interface provides
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index b5fa2ae3116d..f886f2db8153 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -89,16 +89,6 @@ struct vfio_group {
struct blocking_notifier_head notifier;
};

-struct vfio_device {
- refcount_t refcount;
- struct completion comp;
- struct device *dev;
- const struct vfio_device_ops *ops;
- struct vfio_group *group;
- struct list_head group_next;
- void *device_data;
-};
-
#ifdef CONFIG_VFIO_NOIOMMU
static bool noiommu __read_mostly;
module_param_named(enable_unsafe_noiommu_mode,
@@ -532,35 +522,6 @@ static struct vfio_group *vfio_group_get_from_dev(struct device *dev)
/**
* Device objects - create, release, get, put, search
*/
-static
-struct vfio_device *vfio_group_create_device(struct vfio_group *group,
- struct device *dev,
- const struct vfio_device_ops *ops,
- void *device_data)
-{
- struct vfio_device *device;
-
- device = kzalloc(sizeof(*device), GFP_KERNEL);
- if (!device)
- return ERR_PTR(-ENOMEM);
-
- refcount_set(&device->refcount, 1);
- init_completion(&device->comp);
- device->dev = dev;
- /* Our reference on group is moved to the device */
- device->group = group;
- device->ops = ops;
- device->device_data = device_data;
- dev_set_drvdata(dev, device);
-
- mutex_lock(&group->device_lock);
- list_add(&device->group_next, &group->device_list);
- group->dev_counter++;
- mutex_unlock(&group->device_lock);
-
- return device;
-}
-
/* Device reference always implies a group reference */
void vfio_device_put(struct vfio_device *device)
{
@@ -779,14 +740,23 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb,
/**
* VFIO driver API
*/
-int vfio_add_group_dev(struct device *dev,
- const struct vfio_device_ops *ops, void *device_data)
+void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
+ const struct vfio_device_ops *ops, void *device_data)
+{
+ init_completion(&device->comp);
+ device->dev = dev;
+ device->ops = ops;
+ device->device_data = device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_init_group_dev);
+
+int vfio_register_group_dev(struct vfio_device *device)
{
+ struct vfio_device *existing_device;
struct iommu_group *iommu_group;
struct vfio_group *group;
- struct vfio_device *device;

- iommu_group = iommu_group_get(dev);
+ iommu_group = iommu_group_get(device->dev);
if (!iommu_group)
return -EINVAL;

@@ -805,21 +775,50 @@ int vfio_add_group_dev(struct device *dev,
iommu_group_put(iommu_group);
}

- device = vfio_group_get_device(group, dev);
- if (device) {
- dev_WARN(dev, "Device already exists on group %d\n",
+ existing_device = vfio_group_get_device(group, device->dev);
+ if (existing_device) {
+ dev_WARN(device->dev, "Device already exists on group %d\n",
iommu_group_id(iommu_group));
- vfio_device_put(device);
+ vfio_device_put(existing_device);
vfio_group_put(group);
return -EBUSY;
}

- device = vfio_group_create_device(group, dev, ops, device_data);
- if (IS_ERR(device)) {
- vfio_group_put(group);
- return PTR_ERR(device);
- }
+ /* Our reference on group is moved to the device */
+ device->group = group;
+
+ /* Refcounting can't start until the driver calls register */
+ refcount_set(&device->refcount, 1);
+
+ mutex_lock(&group->device_lock);
+ list_add(&device->group_next, &group->device_list);
+ group->dev_counter++;
+ mutex_unlock(&group->device_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(vfio_register_group_dev);
+
+int vfio_add_group_dev(struct device *dev, const struct vfio_device_ops *ops,
+ void *device_data)
+{
+ struct vfio_device *device;
+ int ret;
+
+ device = kzalloc(sizeof(*device), GFP_KERNEL);
+ if (!device)
+ return -ENOMEM;
+
+ vfio_init_group_dev(device, dev, ops, device_data);
+ ret = vfio_register_group_dev(device);
+ if (ret)
+ goto err_kfree;
+ dev_set_drvdata(dev, device);
return 0;
+
+err_kfree:
+ kfree(device);
+ return ret;
}
EXPORT_SYMBOL_GPL(vfio_add_group_dev);

@@ -887,11 +886,9 @@ EXPORT_SYMBOL_GPL(vfio_device_data);
/*
* Decrement the device reference count and wait for the device to be
* removed. Open file descriptors for the device... */
-void *vfio_del_group_dev(struct device *dev)
+void vfio_unregister_group_dev(struct vfio_device *device)
{
- struct vfio_device *device = dev_get_drvdata(dev);
struct vfio_group *group = device->group;
- void *device_data = device->device_data;
struct vfio_unbound_dev *unbound;
unsigned int i = 0;
bool interrupted = false;
@@ -908,7 +905,7 @@ void *vfio_del_group_dev(struct device *dev)
*/
unbound = kzalloc(sizeof(*unbound), GFP_KERNEL);
if (unbound) {
- unbound->dev = dev;
+ unbound->dev = device->dev;
mutex_lock(&group->unbound_lock);
list_add(&unbound->unbound_next, &group->unbound_list);
mutex_unlock(&group->unbound_lock);
@@ -919,7 +916,7 @@ void *vfio_del_group_dev(struct device *dev)
rc = try_wait_for_completion(&device->comp);
while (rc <= 0) {
if (device->ops->request)
- device->ops->request(device_data, i++);
+ device->ops->request(device->device_data, i++);

if (interrupted) {
rc = wait_for_completion_timeout(&device->comp,
@@ -929,7 +926,7 @@ void *vfio_del_group_dev(struct device *dev)
&device->comp, HZ * 10);
if (rc < 0) {
interrupted = true;
- dev_warn(dev,
+ dev_warn(device->dev,
"Device is currently in use, task"
" \"%s\" (%d) "
"blocked until device is released",
@@ -960,11 +957,19 @@ void *vfio_del_group_dev(struct device *dev)
if (list_empty(&group->device_list))
wait_event(group->container_q, !group->container);

- /* Matches the get in vfio_group_create_device() */
+ /* Matches the get in vfio_register_group_dev() */
vfio_group_put(group);
+}
+EXPORT_SYMBOL_GPL(vfio_unregister_group_dev);
+
+void *vfio_del_group_dev(struct device *dev)
+{
+ struct vfio_device *device = dev_get_drvdata(dev);
+ void *device_data = device->device_data;
+
+ vfio_unregister_group_dev(device);
dev_set_drvdata(dev, NULL);
kfree(device);
-
return device_data;
}
EXPORT_SYMBOL_GPL(vfio_del_group_dev);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 38d3c6a8dc7e..f479c5d7f2c3 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -15,6 +15,18 @@
#include <linux/poll.h>
#include <uapi/linux/vfio.h>

+struct vfio_device {
+ struct device *dev;
+ const struct vfio_device_ops *ops;
+ struct vfio_group *group;
+
+ /* Members below here are private, not for driver use */
+ refcount_t refcount;
+ struct completion comp;
+ struct list_head group_next;
+ void *device_data;
+};
+
/**
* struct vfio_device_ops - VFIO bus driver device callbacks
*
@@ -48,11 +60,15 @@ struct vfio_device_ops {
extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
extern void vfio_iommu_group_put(struct iommu_group *group, struct device *dev);

+void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
+ const struct vfio_device_ops *ops, void *device_data);
+int vfio_register_group_dev(struct vfio_device *device);
extern int vfio_add_group_dev(struct device *dev,
const struct vfio_device_ops *ops,
void *device_data);

extern void *vfio_del_group_dev(struct device *dev);
+void vfio_unregister_group_dev(struct vfio_device *device);
extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
extern void vfio_device_put(struct vfio_device *device);
extern void *vfio_device_data(struct vfio_device *device);
--
2.35.1