vfio: Allocate per device file structure

This is preparation for adding vfio device cdev support. vfio device
cdev requires:
1) A per device file memory to store the kvm pointer set by KVM. It will
   be propagated to vfio_device:kvm after the device cdev file is bound
   to an iommufd.
2) A mechanism to block device access through device cdev fd before it
   is bound to an iommufd.

To address the above requirements, this adds a per device file structure
named vfio_device_file. For now, it's only a wrapper of struct vfio_device
pointer. Other fields will be added to this per file structure in future
commits.
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Terrence Xu <terrence.xu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Yanting Jiang <yanting.jiang@intel.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Tested-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20230718135551.6592-2-yi.l.liu@intel.comSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/group.c

@@ -218,19 +218,26 @@ void vfio_device_group_close(struct vfio_device *device)
 
 static struct file *vfio_device_open_file(struct vfio_device *device)
 {
+	struct vfio_device_file *df;
 	struct file *filep;
 	int ret;
 
+	df = vfio_allocate_device_file(device);
+	if (IS_ERR(df)) {
+		ret = PTR_ERR(df);
+		goto err_out;
+	}
+
 	ret = vfio_device_group_open(device);
 	if (ret)
-		goto err_out;
+		goto err_free;
 
 	/*
 	 * We can't use anon_inode_getfd() because we need to modify
 	 * the f_mode flags directly to allow more than just ioctls
 	 */
 	filep = anon_inode_getfile("[vfio-device]", &vfio_device_fops,
-				   device, O_RDWR);
+				   df, O_RDWR);
 	if (IS_ERR(filep)) {
 		ret = PTR_ERR(filep);
 		goto err_close_device;
@@ -254,6 +261,8 @@ static struct file *vfio_device_open_file(struct vfio_device *device)
 
 err_close_device:
 	vfio_device_group_close(device);
+err_free:
+	kfree(df);
 err_out:
 	return ERR_PTR(ret);
 }

drivers/vfio/vfio.h

@@ -16,11 +16,17 @@ struct iommufd_ctx;
 struct iommu_group;
 struct vfio_container;
 
+struct vfio_device_file {
+	struct vfio_device *device;
+};
+
 void vfio_device_put_registration(struct vfio_device *device);
 bool vfio_device_try_get_registration(struct vfio_device *device);
 int vfio_device_open(struct vfio_device *device, struct iommufd_ctx *iommufd);
 void vfio_device_close(struct vfio_device *device,
 		       struct iommufd_ctx *iommufd);
+struct vfio_device_file *
+vfio_allocate_device_file(struct vfio_device *device);
 
 extern const struct file_operations vfio_device_fops;
 

drivers/vfio/vfio_main.c

@@ -419,6 +419,20 @@ static bool vfio_assert_device_open(struct vfio_device *device)
 	return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
 }
 
+struct vfio_device_file *
+vfio_allocate_device_file(struct vfio_device *device)
+{
+	struct vfio_device_file *df;
+
+	df = kzalloc(sizeof(*df), GFP_KERNEL_ACCOUNT);
+	if (!df)
+		return ERR_PTR(-ENOMEM);
+
+	df->device = device;
+
+	return df;
+}
+
 static int vfio_device_first_open(struct vfio_device *device,
 				  struct iommufd_ctx *iommufd)
 {
@@ -532,12 +546,15 @@ static inline void vfio_device_pm_runtime_put(struct vfio_device *device)
  */
 static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 {
-	struct vfio_device *device = filep->private_data;
+	struct vfio_device_file *df = filep->private_data;
+	struct vfio_device *device = df->device;
 
 	vfio_device_group_close(device);
 
 	vfio_device_put_registration(device);
 
+	kfree(df);
+
 	return 0;
 }
 
@@ -1102,7 +1119,8 @@ static int vfio_ioctl_device_feature(struct vfio_device *device,
 static long vfio_device_fops_unl_ioctl(struct file *filep,
 				       unsigned int cmd, unsigned long arg)
 {
-	struct vfio_device *device = filep->private_data;
+	struct vfio_device_file *df = filep->private_data;
+	struct vfio_device *device = df->device;
 	int ret;
 
 	ret = vfio_device_pm_runtime_get(device);
@@ -1129,7 +1147,8 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
 static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf,
 				     size_t count, loff_t *ppos)
 {
-	struct vfio_device *device = filep->private_data;
+	struct vfio_device_file *df = filep->private_data;
+	struct vfio_device *device = df->device;
 
 	if (unlikely(!device->ops->read))
 		return -EINVAL;
@@ -1141,7 +1160,8 @@ static ssize_t vfio_device_fops_write(struct file *filep,
 				      const char __user *buf,
 				      size_t count, loff_t *ppos)
 {
-	struct vfio_device *device = filep->private_data;
+	struct vfio_device_file *df = filep->private_data;
+	struct vfio_device *device = df->device;
 
 	if (unlikely(!device->ops->write))
 		return -EINVAL;
@@ -1151,7 +1171,8 @@ static ssize_t vfio_device_fops_write(struct file *filep,
 
 static int vfio_device_fops_mmap(struct file *filep, struct vm_area_struct *vma)
 {
-	struct vfio_device *device = filep->private_data;
+	struct vfio_device_file *df = filep->private_data;
+	struct vfio_device *device = df->device;
 
 	if (unlikely(!device->ops->mmap))
 		return -EINVAL;