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

Jason Gunthorpe
2022-04-14T18:46:22Z

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