Hi,
On 09/06/2017 23:59, Alex Williamson wrote:
> At the point where the kvm-vfio pseudo device wants to release its
> vfio group reference, we can't always acquire a new reference to make
> that happen. The group can be in a state where we wouldn't allow a
> new reference to be added. This new helper function allows a caller
> to match a file to a group to facilitate this. Given a file and
> group, report if they match. Thus the caller needs to already have a
> group reference to match to the file. This allows the deletion of a
> group without acquiring a new reference.
>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Thanks
Eric
> ---
> drivers/vfio/vfio.c | 9 +++++++++
> include/linux/vfio.h | 2 ++
> virt/kvm/vfio.c | 27 +++++++++++++++++++--------
> 3 files changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index f2e24d5699f2..e6117de60f87 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -1776,6 +1776,15 @@ void vfio_group_put_external_user(struct vfio_group *group)
> }
> EXPORT_SYMBOL_GPL(vfio_group_put_external_user);
>
> +bool vfio_external_group_match_file(struct vfio_group *test_group,
> + struct file *filep)
> +{
> + struct vfio_group *group = filep->private_data;
> +
> + return (filep->f_op == &vfio_group_fops) && (group == test_group);
> +}
> +EXPORT_SYMBOL_GPL(vfio_external_group_match_file);
> +
> int vfio_external_user_iommu_id(struct vfio_group *group)
> {
> return iommu_group_id(group->iommu_group);
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index edf9b2cad277..9b34d0af5d27 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -97,6 +97,8 @@ extern void vfio_unregister_iommu_driver(
> */
> extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
> extern void vfio_group_put_external_user(struct vfio_group *group);
> +extern bool vfio_external_group_match_file(struct vfio_group *group,
> + struct file *filep);
> extern int vfio_external_user_iommu_id(struct vfio_group *group);
> extern long vfio_external_check_extension(struct vfio_group *group,
> unsigned long arg);
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index db9036ef8c73..7c14729b1f2c 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -47,6 +47,22 @@ static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
> return vfio_group;
> }
>
> +static bool kvm_vfio_external_group_match_file(struct vfio_group *group,
> + struct file *filep)
> +{
> + bool ret, (*fn)(struct vfio_group *, struct file *);
> +
> + fn = symbol_get(vfio_external_group_match_file);
> + if (!fn)
> + return false;
> +
> + ret = fn(group, filep);
> +
> + symbol_put(vfio_external_group_match_file);
> +
> + return ret;
> +}
> +
> static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
> {
> void (*fn)(struct vfio_group *);
> @@ -186,18 +202,13 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
> if (!f.file)
> return -EBADF;
>
> - vfio_group = kvm_vfio_group_get_external_user(f.file);
> - fdput(f);
> -
> - if (IS_ERR(vfio_group))
> - return PTR_ERR(vfio_group);
> -
> ret = -ENOENT;
>
> mutex_lock(&kv->lock);
>
> list_for_each_entry(kvg, &kv->group_list, node) {
> - if (kvg->vfio_group != vfio_group)
> + if (!kvm_vfio_external_group_match_file(kvg->vfio_group,
> + f.file))
> continue;
>
> list_del(&kvg->node);
> @@ -211,7 +222,7 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
>
> mutex_unlock(&kv->lock);
>
> - kvm_vfio_group_put_external_user(vfio_group);
> + fdput(f);
>
> kvm_vfio_update_coherency(dev);
>
>
