vfio: support notifier chain in vfio_group

Beyond vfio_iommu events, users might also be interested in
vfio_group events. For example, if a vfio_group is used along
with Qemu/KVM, whenever kvm pointer is set to/cleared from the
vfio_group, users could be notified.

Currently only VFIO_GROUP_NOTIFY_SET_KVM supported.

Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Jike Song <jike.song@intel.com>
[aw: remove use of new typedef]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 6cc2a9ffac10..9901c4671e2f 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -86,6 +86,8 @@ struct vfio_group {
         struct mutex                    unbound_lock;
         atomic_t                        opened;
         bool                            noiommu;
+        struct kvm                      *kvm;
+        struct blocking_notifier_head   notifier;
 };
 
 struct vfio_device {
@@ -339,6 +341,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
 #ifdef CONFIG_VFIO_NOIOMMU
         group->noiommu = (iommu_group_get_iommudata(iommu_group) == &noiommu);
 #endif
+        BLOCKING_INIT_NOTIFIER_HEAD(&group->notifier);
 
         group->nb.notifier_call = vfio_iommu_group_notifier;
 
@@ -1581,6 +1584,9 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep)
 
         filep->private_data = NULL;
 
+        /* Any user didn't unregister? */
+        WARN_ON(group->notifier.head);
+
         vfio_group_try_dissolve_container(group);
 
         atomic_dec(&group->opened);
@@ -2063,6 +2069,76 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
         return ret;
 }
 
+void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
+{
+        group->kvm = kvm;
+        blocking_notifier_call_chain(&group->notifier,
+                                VFIO_GROUP_NOTIFY_SET_KVM, kvm);
+}
+EXPORT_SYMBOL_GPL(vfio_group_set_kvm);
+
+static int vfio_register_group_notifier(struct vfio_group *group,
+                                        unsigned long *events,
+                                        struct notifier_block *nb)
+{
+        struct vfio_container *container;
+        int ret;
+        bool set_kvm = false;
+
+        if (*events & VFIO_GROUP_NOTIFY_SET_KVM)
+                set_kvm = true;
+
+        /* clear known events */
+        *events &= ~VFIO_GROUP_NOTIFY_SET_KVM;
+
+        /* refuse to continue if still events remaining */
+        if (*events)
+                return -EINVAL;
+
+        ret = vfio_group_add_container_user(group);
+        if (ret)
+                return -EINVAL;
+
+        container = group->container;
+        down_read(&container->group_lock);
+
+        ret = blocking_notifier_chain_register(&group->notifier, nb);
+
+        /*
+         * The attaching of kvm and vfio_group might already happen, so
+         * here we replay once upon registration.
+         */
+        if (!ret && set_kvm && group->kvm)
+                blocking_notifier_call_chain(&group->notifier,
+                                        VFIO_GROUP_NOTIFY_SET_KVM, group->kvm);
+
+        up_read(&container->group_lock);
+        vfio_group_try_dissolve_container(group);
+
+        return ret;
+}
+
+static int vfio_unregister_group_notifier(struct vfio_group *group,
+                                         struct notifier_block *nb)
+{
+        struct vfio_container *container;
+        int ret;
+
+        ret = vfio_group_add_container_user(group);
+        if (ret)
+                return -EINVAL;
+
+        container = group->container;
+        down_read(&container->group_lock);
+
+        ret = blocking_notifier_chain_unregister(&group->notifier, nb);
+
+        up_read(&container->group_lock);
+        vfio_group_try_dissolve_container(group);
+
+        return ret;
+}
+
 int vfio_register_notifier(struct device *dev, enum vfio_notify_type type,
                            unsigned long *events, struct notifier_block *nb)
 {
@@ -2080,6 +2156,9 @@ int vfio_register_notifier(struct device *dev, enum vfio_notify_type type,
         case VFIO_IOMMU_NOTIFY:
                 ret = vfio_register_iommu_notifier(group, events, nb);
                 break;
+        case VFIO_GROUP_NOTIFY:
+                ret = vfio_register_group_notifier(group, events, nb);
+                break;
         default:
                 ret = -EINVAL;
         }
@@ -2106,6 +2185,9 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
         case VFIO_IOMMU_NOTIFY:
                 ret = vfio_unregister_iommu_notifier(group, nb);
                 break;
+        case VFIO_GROUP_NOTIFY:
+                ret = vfio_unregister_group_notifier(group, nb);
+                break;
         default:
                 ret = -EINVAL;
         }