Re: [PATCH v0 07/15] mshv: Add ioctl support for MSHV-VFIO bridge device

Stanislav Kinsburskii
2026-01-20T16:13:56Z

On Mon, Jan 19, 2026 at 10:42:22PM -0800, Mukesh R wrote:
> From: Mukesh Rathor <mrathor@linux.microsoft.com>
>
> Add ioctl support for creating MSHV devices for a paritition. At
> present only VFIO device types are supported, but more could be
> added. At a high level, a partition ioctl to create device verifies
> it is of type VFIO and does some setup for bridge code in mshv_vfio.c.
> Adapted from KVM device ioctls.
>
> Credits: Original author: Wei Liu <wei.liu@kernel.org>
> NB: Slightly modified from the original version.
>
> Signed-off-by: Mukesh Rathor <mrathor@linux.microsoft.com>
> ---
> drivers/hv/mshv_root_main.c | 126 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 126 insertions(+)
>
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index 83c7bad269a0..27313419828d 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -1551,6 +1551,129 @@ mshv_partition_ioctl_initialize(struct mshv_partition *partition)
> return ret;
> }
>
> +static long mshv_device_attr_ioctl(struct mshv_device *mshv_dev, int cmd,
> + ulong uarg)
> +{
> + struct mshv_device_attr attr;
> + const struct mshv_device_ops *devops = mshv_dev->device_ops;
> +
> + if (copy_from_user(&attr, (void __user *)uarg, sizeof(attr)))
> + return -EFAULT;
> +
> + switch (cmd) {
> + case MSHV_SET_DEVICE_ATTR:
> + if (devops->device_set_attr)
> + return devops->device_set_attr(mshv_dev, &attr);
> + break;
> + case MSHV_HAS_DEVICE_ATTR:
> + if (devops->device_has_attr)
> + return devops->device_has_attr(mshv_dev, &attr);
> + break;
> + }
> +
> + return -EPERM;
> +}
> +
> +static long mshv_device_fop_ioctl(struct file *filp, unsigned int cmd,
> + ulong uarg)
> +{
> + struct mshv_device *mshv_dev = filp->private_data;
> +
> + switch (cmd) {
> + case MSHV_SET_DEVICE_ATTR:
> + case MSHV_HAS_DEVICE_ATTR:
> + return mshv_device_attr_ioctl(mshv_dev, cmd, uarg);
> + }
> +
> + return -ENOTTY;
> +}
> +
> +static int mshv_device_fop_release(struct inode *inode, struct file *filp)
> +{
> + struct mshv_device *mshv_dev = filp->private_data;
> + struct mshv_partition *partition = mshv_dev->device_pt;
> +
> + if (mshv_dev->device_ops->device_release) {
> + mutex_lock(&partition->pt_mutex);
> + hlist_del(&mshv_dev->device_ptnode);
> + mshv_dev->device_ops->device_release(mshv_dev);
> + mutex_unlock(&partition->pt_mutex);
> + }
> +
> + mshv_partition_put(partition);
> + return 0;
> +}
> +
> +static const struct file_operations mshv_device_fops = {
> + .owner = THIS_MODULE,
> + .unlocked_ioctl = mshv_device_fop_ioctl,
> + .release = mshv_device_fop_release,
> +};
> +
> +long mshv_partition_ioctl_create_device(struct mshv_partition *partition,
> + void __user *uarg)
> +{
> + long rc;
> + struct mshv_create_device devargk;
> + struct mshv_device *mshv_dev;
> + const struct mshv_device_ops *vfio_ops;
> + int type;
> +
> + if (copy_from_user(&devargk, uarg, sizeof(devargk))) {
> + rc = -EFAULT;
> + goto out;
> + }
> +
> + /* At present, only VFIO is supported */
> + if (devargk.type != MSHV_DEV_TYPE_VFIO) {
> + rc = -ENODEV;
> + goto out;
> + }
> +
> + if (devargk.flags & MSHV_CREATE_DEVICE_TEST) {
> + rc = 0;
> + goto out;
> + }
> +
> + mshv_dev = kzalloc(sizeof(*mshv_dev), GFP_KERNEL_ACCOUNT);
> + if (mshv_dev == NULL) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + vfio_ops = &mshv_vfio_device_ops;
> + mshv_dev->device_ops = vfio_ops;
> + mshv_dev->device_pt = partition;
> +
> + rc = vfio_ops->device_create(mshv_dev, type);
> + if (rc < 0) {
> + kfree(mshv_dev);
> + goto out;
> + }
> +
> + hlist_add_head(&mshv_dev->device_ptnode, &partition->pt_devices);
> +
> + mshv_partition_get(partition);
> + rc = anon_inode_getfd(vfio_ops->device_name, &mshv_device_fops,
> + mshv_dev, O_RDWR | O_CLOEXEC);
> + if (rc < 0) {
> + mshv_partition_put(partition);
> + hlist_del(&mshv_dev->device_ptnode);
> + vfio_ops->device_release(mshv_dev);
> + goto out;
> + }
> +
> + devargk.fd = rc;
> + rc = 0;
> +
> + if (copy_to_user(uarg, &devargk, sizeof(devargk))) {

Shouldn't the partition be put here?

Thanks,
Stanislav

> + rc = -EFAULT;
> + goto out;
> + }
> +out:
> + return rc;
> +}
> +
> static long
> mshv_partition_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> {
> @@ -1587,6 +1710,9 @@ mshv_partition_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> case MSHV_ROOT_HVCALL:
> ret = mshv_ioctl_passthru_hvcall(partition, true, uarg);
> break;
> + case MSHV_CREATE_DEVICE:
> + ret = mshv_partition_ioctl_create_device(partition, uarg);
> + break;
> default:
> ret = -ENOTTY;
> }
> --
> 2.51.2.vfs.0.1
>