Cool, thanks!
So we will need only this (to be called from KVM), and that will be it, right?
int vfio_group_iommu_id_from_file(struct file *filep)
...
On 06/22/2013 07:12 AM, Alex Williamson wrote:
> vfio_group_fops_open attempts to limit concurrent sessions by
> disallowing opens once group->container is set. This really doesn't
> do what we want and allow for inconsistent behavior, for instance a
> group can be opened twice, then a container set giving the user two
> file descriptors to the group. But then it won't allow more to be
> opened. There's not much reason to have the group opened multiple
> times since most access is through devices or the container, so
> complete what the original code intended and only allow a single
> instance.
>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> drivers/vfio/vfio.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 6d78736..d30f44d 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -76,6 +76,7 @@ struct vfio_group {
> struct notifier_block nb;
> struct list_head vfio_next;
> struct list_head container_next;
> + atomic_t opened;
> };
>
> struct vfio_device {
> @@ -206,6 +207,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
> INIT_LIST_HEAD(&group->device_list);
> mutex_init(&group->device_lock);
> atomic_set(&group->container_users, 0);
> + atomic_set(&group->opened, 0);
> group->iommu_group = iommu_group;
>
> group->nb.notifier_call = vfio_iommu_group_notifier;
> @@ -1236,12 +1238,22 @@ static long vfio_group_fops_compat_ioctl(struct file *filep,
> static int vfio_group_fops_open(struct inode *inode, struct file *filep)
> {
> struct vfio_group *group;
> + int opened;
>
> group = vfio_group_get_from_minor(iminor(inode));
> if (!group)
> return -ENODEV;
>
> + /* Do we need multiple instances of the group open? Seems not. */
> + opened = atomic_cmpxchg(&group->opened, 0, 1);
> + if (opened) {
> + vfio_group_put(group);
> + return -EBUSY;
> + }
> +
> + /* Is something still in use from a previous open? */
> if (group->container) {
> + atomic_dec(&group->opened);
> vfio_group_put(group);
> return -EBUSY;
> }
> @@ -1259,6 +1271,8 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep)
>
> vfio_group_try_dissolve_container(group);
>
> + atomic_dec(&group->opened);
> +
> vfio_group_put(group);
>
> return 0;
>
--
Alexey
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