Re: [RFC 07/20] iommu/iommufd: Add iommufd_[un]bind_device()

Jason Gunthorpe
2021-09-21T17:14:36Z

On Sun, Sep 19, 2021 at 02:38:35PM +0800, Liu Yi L wrote:

> +/*
> + * A iommufd_device object represents the binding relationship
> + * between iommufd and device. It is created per a successful
> + * binding request from device driver. The bound device must be
> + * a physical device so far. Subdevice will be supported later
> + * (with additional PASID information). An user-assigned cookie
> + * is also recorded to mark the device in the /dev/iommu uAPI.
> + */
> +struct iommufd_device {
> + unsigned int id;
> + struct iommufd_ctx *ictx;
> + struct device *dev; /* always be the physical device */
> + u64 dev_cookie;
> };
>
> static int iommufd_fops_open(struct inode *inode, struct file *filep)
> @@ -32,15 +52,58 @@ static int iommufd_fops_open(struct inode *inode, struct file *filep)
> return -ENOMEM;
>
> refcount_set(&ictx->refs, 1);
> + mutex_init(&ictx->lock);
> + xa_init_flags(&ictx->device_xa, XA_FLAGS_ALLOC);
> filep->private_data = ictx;
>
> return ret;
> }
>
> +static void iommufd_ctx_get(struct iommufd_ctx *ictx)
> +{
> + refcount_inc(&ictx->refs);
> +}

See my earlier remarks about how to structure the lifetime logic, this
ref isn't necessary.

> +static const struct file_operations iommufd_fops;
> +
> +/**
> + * iommufd_ctx_fdget - Acquires a reference to the internal iommufd context.
> + * @fd: [in] iommufd file descriptor.
> + *
> + * Returns a pointer to the iommufd context, otherwise NULL;
> + *
> + */
> +static struct iommufd_ctx *iommufd_ctx_fdget(int fd)
> +{
> + struct fd f = fdget(fd);
> + struct file *file = f.file;
> + struct iommufd_ctx *ictx;
> +
> + if (!file)
> + return NULL;
> +
> + if (file->f_op != &iommufd_fops)
> + return NULL;

Leaks the fdget

> +
> + ictx = file->private_data;
> + if (ictx)
> + iommufd_ctx_get(ictx);

Use success oriented flow

> + fdput(f);
> + return ictx;
> +}

> + */
> +struct iommufd_device *iommufd_bind_device(int fd, struct device *dev,
> + u64 dev_cookie)
> +{
> + struct iommufd_ctx *ictx;
> + struct iommufd_device *idev;
> + unsigned long index;
> + unsigned int id;
> + int ret;
> +
> + ictx = iommufd_ctx_fdget(fd);
> + if (!ictx)
> + return ERR_PTR(-EINVAL);
> +
> + mutex_lock(&ictx->lock);
> +
> + /* check duplicate registration */
> + xa_for_each(&ictx->device_xa, index, idev) {
> + if (idev->dev == dev || idev->dev_cookie == dev_cookie) {
> + idev = ERR_PTR(-EBUSY);
> + goto out_unlock;
> + }

I can't think of a reason why this expensive check is needed.

> + }
> +
> + idev = kzalloc(sizeof(*idev), GFP_KERNEL);
> + if (!idev) {
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + /* Establish the security context */
> + ret = iommu_device_init_user_dma(dev, (unsigned long)ictx);
> + if (ret)
> + goto out_free;
> +
> + ret = xa_alloc(&ictx->device_xa, &id, idev,
> + XA_LIMIT(IOMMUFD_DEVID_MIN, IOMMUFD_DEVID_MAX),
> + GFP_KERNEL);

idev should be fully initialized before being placed in the xarray, so
this should be the last thing done.

Why not just use the standard xa_limit_32b instead of special single
use constants?

Jason