[PATCH v3 16/18] vfio: Remove iommu group notifier

Lu Baolu
2021-12-06T02:03:30Z

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>
---
drivers/vfio/vfio.c | 147 --------------------------------------------
1 file changed, 147 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 5c81346367b1..33d984ff3cc5 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -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;
@@ -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);

/**
@@ -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? */
@@ -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;
@@ -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);
}

@@ -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
*/
--
2.25.1