[PATCH v2 3/8] vfio: Change vfio_external_user_iommu_id() to vfio_file_iommu_group()

Jason Gunthorpe
2022-04-20T19:23:34Z

The only user wants to get a pointer to the struct iommu_group associated
with the VFIO group 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, the vfio_group
and thus the iommu_group cannot be destroyed while the group file is open.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/vfio/vfio.c | 21 ++++++++++++++-------
include/linux/vfio.h | 2 +-
virt/kvm/vfio.c | 37 ++++++++++++-------------------------
3 files changed, 27 insertions(+), 33 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index a4555014bd1e72..3444d36714e933 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 +1998,21 @@ 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 group file
+ * @file: VFIO group file
+ *
+ * The returned iommu_group is valid as long as a ref is held on the file.
+ */
+struct iommu_group *vfio_file_iommu_group(struct file *file)
{
- return iommu_group_id(group->iommu_group);
+ struct vfio_group *group = file->private_data;
+
+ if (file->f_op != &vfio_group_fops)
+ return NULL;
+ return group->iommu_group;
}
-EXPORT_SYMBOL_GPL(vfio_external_user_iommu_id);
+EXPORT_SYMBOL_GPL(vfio_file_iommu_group);

long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
{
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 66dda06ec42d1b..8b53fd9920d24a 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -144,7 +144,7 @@ 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 struct iommu_group *vfio_file_iommu_group(struct file *file);
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 07ee54a62b560d..1655d3aebd16b4 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -108,43 +108,31 @@ static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
}

#ifdef CONFIG_SPAPR_TCE_IOMMU
-static int kvm_vfio_external_user_iommu_id(struct vfio_group *vfio_group)
+static struct iommu_group *kvm_vfio_file_iommu_group(struct file *file)
{
- int (*fn)(struct vfio_group *);
- int ret = -EINVAL;
+ struct iommu_group *(*fn)(struct file *file);
+ struct iommu_group *ret;

- fn = symbol_get(vfio_external_user_iommu_id);
+ fn = symbol_get(vfio_file_iommu_group);
if (!fn)
- return ret;
+ return NULL;

- ret = fn(vfio_group);
+ ret = fn(file);

- symbol_put(vfio_external_user_iommu_id);
+ symbol_put(vfio_file_iommu_group);

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 = kvm_vfio_group_get_iommu_group(vfio_group);
+ struct iommu_group *grp = kvm_vfio_file_iommu_group(kvg->file);

if (WARN_ON_ONCE(!grp))
return;

kvm_spapr_tce_release_iommu_group(kvm, grp);
- iommu_group_put(grp);
}
#endif

@@ -258,7 +246,7 @@ static int kvm_vfio_group_del(struct kvm_device *dev, unsigned int fd)
list_del(&kvg->node);
kvm_arch_end_assignment(dev->kvm);
#ifdef CONFIG_SPAPR_TCE_IOMMU
- kvm_spapr_tce_release_vfio_group(dev->kvm, kvg->vfio_group);
+ kvm_spapr_tce_release_vfio_group(dev->kvm, kvg);
#endif
kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
kvm_vfio_group_put_external_user(kvg->vfio_group);
@@ -304,7 +292,7 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
if (kvg->file != f.file)
continue;

- grp = kvm_vfio_group_get_iommu_group(kvg->vfio_group);
+ grp = kvm_vfio_file_iommu_group(kvg->file);
if (WARN_ON_ONCE(!grp)) {
ret = -EIO;
goto err_fdput;
@@ -312,7 +300,6 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,

ret = kvm_spapr_tce_attach_iommu_group(dev->kvm, param.tablefd,
grp);
- iommu_group_put(grp);
break;
}

@@ -386,7 +373,7 @@ static void kvm_vfio_destroy(struct kvm_device *dev)

list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
#ifdef CONFIG_SPAPR_TCE_IOMMU
- kvm_spapr_tce_release_vfio_group(dev->kvm, kvg->vfio_group);
+ kvm_spapr_tce_release_vfio_group(dev->kvm, kvg);
#endif
kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
kvm_vfio_group_put_external_user(kvg->vfio_group);
--
2.36.0