diff options
Diffstat (limited to 'drivers/vfio/vfio.c')
| -rw-r--r-- | drivers/vfio/vfio.c | 119 |
1 files changed, 104 insertions, 15 deletions
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index f018d8d0f975..4cde85501444 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -63,6 +63,11 @@ struct vfio_container { void *iommu_data; }; +struct vfio_unbound_dev { + struct device *dev; + struct list_head unbound_next; +}; + struct vfio_group { struct kref kref; int minor; @@ -75,6 +80,8 @@ struct vfio_group { struct notifier_block nb; struct list_head vfio_next; struct list_head container_next; + struct list_head unbound_list; + struct mutex unbound_lock; atomic_t opened; }; @@ -204,6 +211,8 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group) kref_init(&group->kref); INIT_LIST_HEAD(&group->device_list); mutex_init(&group->device_lock); + INIT_LIST_HEAD(&group->unbound_list); + mutex_init(&group->unbound_lock); atomic_set(&group->container_users, 0); atomic_set(&group->opened, 0); group->iommu_group = iommu_group; @@ -264,13 +273,22 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group) static void vfio_group_release(struct kref *kref) { struct vfio_group *group = container_of(kref, struct vfio_group, kref); + struct vfio_unbound_dev *unbound, *tmp; + struct iommu_group *iommu_group = group->iommu_group; WARN_ON(!list_empty(&group->device_list)); + list_for_each_entry_safe(unbound, tmp, + &group->unbound_list, unbound_next) { + list_del(&unbound->unbound_next); + kfree(unbound); + } + device_destroy(vfio.class, MKDEV(MAJOR(vfio.group_devt), group->minor)); list_del(&group->vfio_next); vfio_free_group_minor(group->minor); vfio_group_unlock_and_free(group); + iommu_group_put(iommu_group); } static void vfio_group_put(struct vfio_group *group) @@ -440,17 +458,36 @@ static bool vfio_whitelisted_driver(struct device_driver *drv) } /* - * A vfio group is viable for use by userspace if all devices are either - * driver-less or bound to a vfio or whitelisted driver. We test the - * latter by the existence of a struct vfio_device matching the dev. + * 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 a whitelisted driver + * + * 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 = ACCESS_ONCE(dev->driver); + struct vfio_unbound_dev *unbound; + int ret = -EINVAL; - if (!drv || vfio_whitelisted_driver(drv)) + mutex_lock(&group->unbound_lock); + list_for_each_entry(unbound, &group->unbound_list, unbound_next) { + if (dev == unbound->dev) { + ret = 0; + break; + } + } + mutex_unlock(&group->unbound_lock); + + if (!ret || !drv || vfio_whitelisted_driver(drv)) return 0; device = vfio_group_get_device(group, dev); @@ -459,7 +496,7 @@ static int vfio_dev_viable(struct device *dev, void *data) return 0; } - return -EINVAL; + return ret; } /** @@ -501,6 +538,7 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb, { struct vfio_group *group = container_of(nb, struct vfio_group, nb); struct device *dev = data; + struct vfio_unbound_dev *unbound; /* * Need to go through a group_lock lookup to get a reference or we @@ -550,6 +588,17 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb, * stop the system to maintain isolation. At a minimum, we'd * want a toggle to disable driver auto probe for this device. */ + + mutex_lock(&group->unbound_lock); + list_for_each_entry(unbound, + &group->unbound_list, unbound_next) { + if (dev == unbound->dev) { + list_del(&unbound->unbound_next); + kfree(unbound); + break; + } + } + mutex_unlock(&group->unbound_lock); break; } @@ -578,6 +627,12 @@ int vfio_add_group_dev(struct device *dev, iommu_group_put(iommu_group); return PTR_ERR(group); } + } else { + /* + * A found vfio_group already holds a reference to the + * iommu_group. A created vfio_group keeps the reference. + */ + iommu_group_put(iommu_group); } device = vfio_group_get_device(group, dev); @@ -586,21 +641,19 @@ int vfio_add_group_dev(struct device *dev, dev_name(dev), iommu_group_id(iommu_group)); vfio_device_put(device); vfio_group_put(group); - iommu_group_put(iommu_group); return -EBUSY; } device = vfio_group_create_device(group, dev, ops, device_data); if (IS_ERR(device)) { vfio_group_put(group); - iommu_group_put(iommu_group); return PTR_ERR(device); } /* - * Added device holds reference to iommu_group and vfio_device - * (which in turn holds reference to vfio_group). Drop extra - * group reference used while acquiring device. + * Drop all but the vfio_device reference. The vfio_device holds + * a reference to the vfio_group, which holds a reference to the + * iommu_group. */ vfio_group_put(group); @@ -655,8 +708,9 @@ void *vfio_del_group_dev(struct device *dev) { struct vfio_device *device = dev_get_drvdata(dev); struct vfio_group *group = device->group; - struct iommu_group *iommu_group = group->iommu_group; void *device_data = device->device_data; + struct vfio_unbound_dev *unbound; + unsigned int i = 0; /* * The group exists so long as we have a device reference. Get @@ -664,14 +718,49 @@ void *vfio_del_group_dev(struct device *dev) */ vfio_group_get(group); + /* + * When the device is removed from the group, the group suddenly + * becomes non-viable; the device has a driver (until the unbind + * completes), but it's not present in the group. This is bad news + * for any external users that need to re-acquire a group reference + * in order to match and release their existing reference. To + * solve this, we track such devices on the unbound_list to bridge + * the gap until they're fully unbound. + */ + unbound = kzalloc(sizeof(*unbound), GFP_KERNEL); + if (unbound) { + unbound->dev = dev; + mutex_lock(&group->unbound_lock); + list_add(&unbound->unbound_next, &group->unbound_list); + mutex_unlock(&group->unbound_lock); + } + WARN_ON(!unbound); + vfio_device_put(device); - /* TODO send a signal to encourage this to be released */ - wait_event(vfio.release_q, !vfio_dev_present(group, dev)); + /* + * If the device is still present in the group after the above + * 'put', then it is in use and we need to request it from the + * bus driver. The driver may in turn need to request the + * device from the user. We send the request on an arbitrary + * interval with counter to allow the driver to take escalating + * measures to release the device if it has the ability to do so. + */ + do { + device = vfio_group_get_device(group, dev); + if (!device) + break; - vfio_group_put(group); + if (device->ops->request) + device->ops->request(device_data, i++); - iommu_group_put(iommu_group); + vfio_device_put(device); + + } while (wait_event_interruptible_timeout(vfio.release_q, + !vfio_dev_present(group, dev), + HZ * 10) <= 0); + + vfio_group_put(group); return device_data; } |