vfio: New external user group/file match

At the point where the kvm-vfio pseudo device wants to release its
vfio group reference, we can't always acquire a new reference to make
that happen.  The group can be in a state where we wouldn't allow a
new reference to be added.  This new helper function allows a caller
to match a file to a group to facilitate this.  Given a file and
group, report if they match.  Thus the caller needs to already have a
group reference to match to the file.  This allows the deletion of a
group without acquiring a new reference.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 54dd2fbf83d925ba7df0db1ae412acc5d64400c9..7597a377eb4e459cee02d74e09a320b0f55b0526 100644 (file)
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1776,6 +1776,15 @@ void vfio_group_put_external_user(struct vfio_group *group)
 }
 EXPORT_SYMBOL_GPL(vfio_group_put_external_user);
 
+bool vfio_external_group_match_file(struct vfio_group *test_group,
+                                   struct file *filep)
+{
+       struct vfio_group *group = filep->private_data;
+
+       return (filep->f_op == &vfio_group_fops) && (group == test_group);
+}
+EXPORT_SYMBOL_GPL(vfio_external_group_match_file);
+
 int vfio_external_user_iommu_id(struct vfio_group *group)
 {
        return iommu_group_id(group->iommu_group);

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index edf9b2cad277d95d5b4b2ffd4b3202d2abd14f70..9b34d0af5d275d41f189cca7445561b7b1415df0 100644 (file)
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -97,6 +97,8 @@ extern void vfio_unregister_iommu_driver(
  */
 extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
 extern void vfio_group_put_external_user(struct vfio_group *group);
+extern bool vfio_external_group_match_file(struct vfio_group *group,
+                                          struct file *filep);
 extern int vfio_external_user_iommu_id(struct vfio_group *group);
 extern long vfio_external_check_extension(struct vfio_group *group,
                                          unsigned long arg);

diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 6e002d0f31910dc3098cc798eff1127e268a249f..d99850c462a1879e0a530c387ad4f756d0e64227 100644 (file)
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -51,6 +51,22 @@ static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
        return vfio_group;
 }
 
+static bool kvm_vfio_external_group_match_file(struct vfio_group *group,
+                                              struct file *filep)
+{
+       bool ret, (*fn)(struct vfio_group *, struct file *);
+
+       fn = symbol_get(vfio_external_group_match_file);
+       if (!fn)
+               return false;
+
+       ret = fn(group, filep);
+
+       symbol_put(vfio_external_group_match_file);
+
+       return ret;
+}
+
 static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
 {
        void (*fn)(struct vfio_group *);
@@ -231,18 +247,13 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
                if (!f.file)
                        return -EBADF;
 
-               vfio_group = kvm_vfio_group_get_external_user(f.file);
-               fdput(f);
-
-               if (IS_ERR(vfio_group))
-                       return PTR_ERR(vfio_group);
-
                ret = -ENOENT;
 
                mutex_lock(&kv->lock);
 
                list_for_each_entry(kvg, &kv->group_list, node) {
-                       if (kvg->vfio_group != vfio_group)
+                       if (!kvm_vfio_external_group_match_file(kvg->vfio_group,
+                                                               f.file))
                                continue;
 
                        list_del(&kvg->node);
@@ -260,7 +271,7 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
 
                mutex_unlock(&kv->lock);
 
-               kvm_vfio_group_put_external_user(vfio_group);
+               fdput(f);
 
                kvm_vfio_update_coherency(dev);