[PATCH 05/10] vfio: Move vfio_external_user_iommu_id() to vfio_file_ops

[Jason Gunthorpe <jgg@nvidia.com>]

The only user wants to get a pointer to the struct iommu_group associated
with the VFIO file being used. Instead of returning the group ID then
searching sysfs for that string just directly return the iommu_group
pointer already held by the vfio_group struct.

It already has a safe lifetime due to the struct file kref.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/vfio/vfio.c  | 20 ++++++++-----
 include/linux/vfio.h |  2 +-
 virt/kvm/vfio.c      | 68 ++++++--------------------------------------
 3 files changed, 22 insertions(+), 68 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 93508f6a8beda5..4d62de69705573 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1919,10 +1919,7 @@ static const struct file_operations vfio_device_fops = {
  * increments the container user counter to prevent
  * the VFIO group from disposal before KVM exits.
  *
- * 3. The external user calls vfio_external_user_iommu_id()
- * to know an IOMMU ID.
- *
- * 4. When the external KVM finishes, it calls
+ * 3. When the external KVM finishes, it calls
  * vfio_group_put_external_user() to release the VFIO group.
  * This call decrements the container user counter.
  */
@@ -2001,11 +1998,19 @@ bool vfio_external_group_match_file(struct vfio_group *test_group,
 }
 EXPORT_SYMBOL_GPL(vfio_external_group_match_file);
 
-int vfio_external_user_iommu_id(struct vfio_group *group)
+/**
+ * vfio_file_iommu_group - Return the struct iommu_group for the vfio file
+ * @filep: VFIO file
+ *
+ * The returned iommu_group is valid as long as a ref is held on the filep.
+ * VFIO files always have an iommu_group, so this cannot fail.
+ */
+static struct iommu_group *vfio_file_iommu_group(struct file *filep)
 {
-	return iommu_group_id(group->iommu_group);
+	struct vfio_group *group = filep->private_data;
+
+	return group->iommu_group;
 }
-EXPORT_SYMBOL_GPL(vfio_external_user_iommu_id);
 
 long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
 {
@@ -2014,6 +2019,7 @@ long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
 EXPORT_SYMBOL_GPL(vfio_external_check_extension);
 
 static const struct vfio_file_ops vfio_file_group_ops = {
+	.get_iommu_group = vfio_file_iommu_group,
 };
 
 /**
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 409bbf817206cc..e5ca7d5a0f1584 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -139,6 +139,7 @@ int vfio_mig_get_next_state(struct vfio_device *device,
  * External user API
  */
 struct vfio_file_ops {
+	struct iommu_group *(*get_iommu_group)(struct file *filep);
 };
 extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
 extern void vfio_group_put_external_user(struct vfio_group *group);
@@ -146,7 +147,6 @@ extern struct vfio_group *vfio_group_get_external_user_from_dev(struct device
 								*dev);
 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);
 const struct vfio_file_ops *vfio_file_get_ops(struct file *filep);
diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 254d8c18378163..743e4870fa1825 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -118,47 +118,14 @@ static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
 	return ret > 0;
 }
 
-static int kvm_vfio_external_user_iommu_id(struct vfio_group *vfio_group)
-{
-	int (*fn)(struct vfio_group *);
-	int ret = -EINVAL;
-
-	fn = symbol_get(vfio_external_user_iommu_id);
-	if (!fn)
-		return ret;
-
-	ret = fn(vfio_group);
-
-	symbol_put(vfio_external_user_iommu_id);
-
-	return ret;
-}
-
-static struct iommu_group *kvm_vfio_group_get_iommu_group(
-		struct vfio_group *group)
-{
-	int group_id = kvm_vfio_external_user_iommu_id(group);
-
-	if (group_id < 0)
-		return NULL;
-
-	return iommu_group_get_by_id(group_id);
-}
-
 static void kvm_spapr_tce_release_vfio_group(struct kvm *kvm,
-		struct vfio_group *vfio_group)
+					     struct kvm_vfio_group *kvg)
 {
-	struct iommu_group *grp;
-
 	if (!IS_ENABLED(CONFIG_SPAPR_TCE_IOMMU))
 		return;
 
-	grp = kvm_vfio_group_get_iommu_group(vfio_group);
-	if (WARN_ON_ONCE(!grp))
-		return;
-
-	kvm_spapr_tce_release_iommu_group(kvm, grp);
-	iommu_group_put(grp);
+	kvm_spapr_tce_release_iommu_group(kvm,
+					  kvg->ops->get_iommu_group(kvg->filp));
 }
 
 /*
@@ -283,7 +250,7 @@ static int kvm_vfio_group_del(struct kvm_device *dev, unsigned int fd)
 
 		list_del(&kvg->node);
 		kvm_arch_end_assignment(dev->kvm);
-		kvm_spapr_tce_release_vfio_group(dev->kvm, kvg->vfio_group);
+		kvm_spapr_tce_release_vfio_group(dev->kvm, kvg);
 		kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
 		kvm_vfio_group_put_external_user(kvg->vfio_group);
 		fput(kvg->filp);
@@ -306,10 +273,8 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
 {
 	struct kvm_vfio_spapr_tce param;
 	struct kvm_vfio *kv = dev->private;
-	struct vfio_group *vfio_group;
 	struct kvm_vfio_group *kvg;
 	struct fd f;
-	struct iommu_group *grp;
 	int ret;
 
 	if (!IS_ENABLED(CONFIG_SPAPR_TCE_IOMMU))
@@ -322,18 +287,6 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
 	if (!f.file)
 		return -EBADF;
 
-	vfio_group = kvm_vfio_group_get_external_user(f.file);
-	if (IS_ERR(vfio_group)) {
-		ret = PTR_ERR(vfio_group);
-		goto err_fdput;
-	}
-
-	grp = kvm_vfio_group_get_iommu_group(vfio_group);
-	if (WARN_ON_ONCE(!grp)) {
-		ret = -EIO;
-		goto err_put_external;
-	}
-
 	ret = -ENOENT;
 
 	mutex_lock(&kv->lock);
@@ -341,18 +294,13 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
 	list_for_each_entry(kvg, &kv->group_list, node) {
 		if (kvg->filp != f.file)
 			continue;
-
-		ret = kvm_spapr_tce_attach_iommu_group(dev->kvm, param.tablefd,
-						       grp);
+		ret = kvm_spapr_tce_attach_iommu_group(
+			dev->kvm, param.tablefd,
+			kvg->ops->get_iommu_group(kvg->filp));
 		break;
 	}
 
 	mutex_unlock(&kv->lock);
-
-	iommu_group_put(grp);
-err_put_external:
-	kvm_vfio_group_put_external_user(vfio_group);
-err_fdput:
 	fdput(f);
 	return ret;
 }
@@ -418,7 +366,7 @@ static void kvm_vfio_destroy(struct kvm_device *dev)
 	struct kvm_vfio_group *kvg, *tmp;
 
 	list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
-		kvm_spapr_tce_release_vfio_group(dev->kvm, kvg->vfio_group);
+		kvm_spapr_tce_release_vfio_group(dev->kvm, kvg);
 		kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
 		kvm_vfio_group_put_external_user(kvg->vfio_group);
 		fput(kvg->filp);
-- 
2.35.1