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

Mukesh R
2026-04-18T00:20:59Z

On 1/20/26 08:13, Stanislav Kinsburskii wrote:
> 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?

No. anon_inode_getfd was successful and so it installed the fd already..
As a result the cleanup will happen in the file op release.

Thanks,
-Mukesh

> 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
>>