[PATCH v5 02/29] iommufd: Introduce iommufd_object_alloc_ucmd helper

Nicolin Chen
2025-05-18T03:30:40Z

An object allocator needs to call either iommufd_object_finalize() upon a
success or iommufd_object_abort_and_destroy() upon an error code.

To reduce duplication, store a new_obj in the struct iommufd_ucmd and call
iommufd_object_finalize/iommufd_object_abort_and_destroy() accordingly in
the main function.

This will also ease a driver-allocated object so that a driver can simply
return with an error code to trigger an iommufd_object_abort_and_destroy()
instead of doing an abort itself.

Similar to iommufd_object_alloc() and __iommufd_object_alloc(), add a pair
of helpers: __iommufd_object_alloc_ucmd() and iommufd_object_alloc_ucmd().

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/iommufd/iommufd_private.h | 1 +
include/linux/iommufd.h | 23 +++++++++++++++++++++++
drivers/iommu/iommufd/driver.c | 18 ++++++++++++++++++
drivers/iommu/iommufd/main.c | 7 +++++++
4 files changed, 49 insertions(+)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 10899e2cd34a..16767c231580 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -135,6 +135,7 @@ struct iommufd_ucmd {
void __user *ubuffer;
u32 user_size;
void *cmd;
+ struct iommufd_object *new_obj;
};

int iommufd_vfio_ioctl(struct iommufd_ctx *ictx, unsigned int cmd,
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 498c9a768506..47f38034f5e7 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -22,6 +22,7 @@ struct iommu_user_data_array;
struct iommufd_access;
struct iommufd_ctx;
struct iommufd_device;
+struct iommufd_ucmd;
struct iommufd_viommu_ops;
struct page;

@@ -51,6 +52,18 @@ struct iommufd_object {
unsigned int id;
};

+#define __iommufd_object_alloc_ucmd(ucmd, ptr, type, obj) \
+ container_of(_iommufd_object_alloc_ucmd( \
+ ucmd, \
+ sizeof(*(ptr)) + BUILD_BUG_ON_ZERO( \
+ offsetof(typeof(*(ptr)), \
+ obj) != 0), \
+ type), \
+ typeof(*(ptr)), obj)
+
+#define iommufd_object_alloc_ucmd(ucmd, ptr, type) \
+ __iommufd_object_alloc_ucmd(ucmd, ptr, type, obj)
+
struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
struct device *dev, u32 *id);
void iommufd_device_unbind(struct iommufd_device *idev);
@@ -193,6 +206,9 @@ static inline int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx)
struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type);
+struct iommufd_object *
+_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd, size_t size,
+ enum iommufd_object_type type);
struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
unsigned long vdev_id);
int iommufd_viommu_get_vdev_id(struct iommufd_viommu *viommu,
@@ -208,6 +224,13 @@ _iommufd_object_alloc(struct iommufd_ctx *ictx, size_t size,
return ERR_PTR(-EOPNOTSUPP);
}

+static inline struct iommufd_object *
+_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd, size_t size,
+ enum iommufd_object_type type)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
static inline struct device *
iommufd_viommu_find_dev(struct iommufd_viommu *viommu, unsigned long vdev_id)
{
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index 922cd1fe7ec2..28dec9e09720 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -36,6 +36,24 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
}
EXPORT_SYMBOL_NS_GPL(_iommufd_object_alloc, "IOMMUFD");

+struct iommufd_object *_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd,
+ size_t size,
+ enum iommufd_object_type type)
+{
+ struct iommufd_object *new_obj;
+
+ if (ucmd->new_obj)
+ return ERR_PTR(-EBUSY);
+
+ new_obj = _iommufd_object_alloc(ucmd->ictx, size, type);
+ if (IS_ERR(new_obj))
+ return new_obj;
+
+ ucmd->new_obj = new_obj;
+ return new_obj;
+}
+EXPORT_SYMBOL_NS_GPL(_iommufd_object_alloc_ucmd, "IOMMUFD");
+
/* Caller should xa_lock(&viommu->vdevs) to protect the return value */
struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
unsigned long vdev_id)
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 347c56ef44d8..c6d0b446e632 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -416,6 +416,13 @@ static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
if (ret)
return ret;
ret = op->execute(&ucmd);
+
+ if (ucmd.new_obj) {
+ if (ret)
+ iommufd_object_abort_and_destroy(ictx, ucmd.new_obj);
+ else
+ iommufd_object_finalize(ictx, ucmd.new_obj);
+ }
return ret;
}

--
2.43.0