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vfio: Remove iommu group notifier
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The iommu core and driver core have been enhanced to avoid unsafe driver
binding to a live group after iommu_group_set_dma_owner(PRIVATE_USER)
has been called. There's no need to register iommu group notifier. This
removes the iommu group notifer which contains BUG_ON() and WARN().

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/r/20220418005000.897664-11-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
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Lu Baolu authored and Joerg Roedel committed Apr 28, 2022
1 parent 93219ea commit 3b86f31
Showing 1 changed file with 0 additions and 147 deletions.
147 changes: 0 additions & 147 deletions drivers/vfio/vfio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,6 @@ struct vfio_group {
struct vfio_container *container;
struct list_head device_list;
struct mutex device_lock;
struct notifier_block nb;
struct list_head vfio_next;
struct list_head container_next;
atomic_t opened;
Expand Down Expand Up @@ -274,8 +273,6 @@ void vfio_unregister_iommu_driver(const struct vfio_iommu_driver_ops *ops)
}
EXPORT_SYMBOL_GPL(vfio_unregister_iommu_driver);

static int vfio_iommu_group_notifier(struct notifier_block *nb,
unsigned long action, void *data);
static void vfio_group_get(struct vfio_group *group);

/*
Expand Down Expand Up @@ -395,13 +392,6 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group,
goto err_put;
}

group->nb.notifier_call = vfio_iommu_group_notifier;
err = iommu_group_register_notifier(iommu_group, &group->nb);
if (err) {
ret = ERR_PTR(err);
goto err_put;
}

mutex_lock(&vfio.group_lock);

/* Did we race creating this group? */
Expand All @@ -422,7 +412,6 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group,

err_unlock:
mutex_unlock(&vfio.group_lock);
iommu_group_unregister_notifier(group->iommu_group, &group->nb);
err_put:
put_device(&group->dev);
return ret;
Expand All @@ -447,7 +436,6 @@ static void vfio_group_put(struct vfio_group *group)
cdev_device_del(&group->cdev, &group->dev);
mutex_unlock(&vfio.group_lock);

iommu_group_unregister_notifier(group->iommu_group, &group->nb);
put_device(&group->dev);
}

Expand Down Expand Up @@ -503,141 +491,6 @@ static struct vfio_device *vfio_group_get_device(struct vfio_group *group,
return NULL;
}

/*
* Some drivers, like pci-stub, are only used to prevent other drivers from
* claiming a device and are therefore perfectly legitimate for a user owned
* group. The pci-stub driver has no dependencies on DMA or the IOVA mapping
* of the device, but it does prevent the user from having direct access to
* the device, which is useful in some circumstances.
*
* We also assume that we can include PCI interconnect devices, ie. bridges.
* IOMMU grouping on PCI necessitates that if we lack isolation on a bridge
* then all of the downstream devices will be part of the same IOMMU group as
* the bridge. Thus, if placing the bridge into the user owned IOVA space
* breaks anything, it only does so for user owned devices downstream. Note
* that error notification via MSI can be affected for platforms that handle
* MSI within the same IOVA space as DMA.
*/
static const char * const vfio_driver_allowed[] = { "pci-stub" };

static bool vfio_dev_driver_allowed(struct device *dev,
struct device_driver *drv)
{
if (dev_is_pci(dev)) {
struct pci_dev *pdev = to_pci_dev(dev);

if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
return true;
}

return match_string(vfio_driver_allowed,
ARRAY_SIZE(vfio_driver_allowed),
drv->name) >= 0;
}

/*
* A vfio group is viable for use by userspace if all devices are in
* one of the following states:
* - driver-less
* - bound to a vfio driver
* - bound to an otherwise allowed driver
* - a PCI interconnect device
*
* We use two methods to determine whether a device is bound to a vfio
* driver. The first is to test whether the device exists in the vfio
* group. The second is to test if the device exists on the group
* unbound_list, indicating it's in the middle of transitioning from
* a vfio driver to driver-less.
*/
static int vfio_dev_viable(struct device *dev, void *data)
{
struct vfio_group *group = data;
struct vfio_device *device;
struct device_driver *drv = READ_ONCE(dev->driver);

if (!drv || vfio_dev_driver_allowed(dev, drv))
return 0;

device = vfio_group_get_device(group, dev);
if (device) {
vfio_device_put(device);
return 0;
}

return -EINVAL;
}

/*
* Async device support
*/
static int vfio_group_nb_add_dev(struct vfio_group *group, struct device *dev)
{
struct vfio_device *device;

/* Do we already know about it? We shouldn't */
device = vfio_group_get_device(group, dev);
if (WARN_ON_ONCE(device)) {
vfio_device_put(device);
return 0;
}

/* Nothing to do for idle groups */
if (!atomic_read(&group->container_users))
return 0;

/* TODO Prevent device auto probing */
dev_WARN(dev, "Device added to live group %d!\n",
iommu_group_id(group->iommu_group));

return 0;
}

static int vfio_group_nb_verify(struct vfio_group *group, struct device *dev)
{
/* We don't care what happens when the group isn't in use */
if (!atomic_read(&group->container_users))
return 0;

return vfio_dev_viable(dev, group);
}

static int vfio_iommu_group_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
struct vfio_group *group = container_of(nb, struct vfio_group, nb);
struct device *dev = data;

switch (action) {
case IOMMU_GROUP_NOTIFY_ADD_DEVICE:
vfio_group_nb_add_dev(group, dev);
break;
case IOMMU_GROUP_NOTIFY_DEL_DEVICE:
/*
* Nothing to do here. If the device is in use, then the
* vfio sub-driver should block the remove callback until
* it is unused. If the device is unused or attached to a
* stub driver, then it should be released and we don't
* care that it will be going away.
*/
break;
case IOMMU_GROUP_NOTIFY_BIND_DRIVER:
dev_dbg(dev, "%s: group %d binding to driver\n", __func__,
iommu_group_id(group->iommu_group));
break;
case IOMMU_GROUP_NOTIFY_BOUND_DRIVER:
dev_dbg(dev, "%s: group %d bound to driver %s\n", __func__,
iommu_group_id(group->iommu_group), dev->driver->name);
BUG_ON(vfio_group_nb_verify(group, dev));
break;
case IOMMU_GROUP_NOTIFY_UNBIND_DRIVER:
dev_dbg(dev, "%s: group %d unbinding from driver %s\n",
__func__, iommu_group_id(group->iommu_group),
dev->driver->name);
break;
}
return NOTIFY_OK;
}

/*
* VFIO driver API
*/
Expand Down

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