On Thu, 2013-03-21 at 18:48 +1100, Alexey Kardashevskiy wrote:
> As IOMMU groups are exposed to the user space by their numbers,
> the user space can use them in various kernel APIs so the kernel
> might need an API to find a group by its ID.
>
> As an example, QEMU VFIO on PPC64 platform needs it to associate
> a logical bus number (LIOBN) with a specific IOMMU group in order
> to support in-kernel handling of DMA map/unmap requests.
>
> The patch adds the iommu_group_find(id) function which performs
> such search.
>
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
> drivers/iommu/iommu.c | 26 ++++++++++++++++++++++++++
> include/linux/iommu.h | 1 +
> 2 files changed, 27 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index b0afd3d..6340cac 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -205,6 +205,32 @@ printk("%s %u grp %d\n", __func__, __LINE__,
> iommu_group_id(group));
> }
> EXPORT_SYMBOL_GPL(iommu_group_alloc);
>
> +struct iommu_group *iommu_group_find(int id)
> +{
> + struct kobject *group_kobj;
> + struct iommu_group *grp;
> + const char *name;
> +
> + if (!iommu_group_kset)
> + return NULL;
> +
> + name = kasprintf(GFP_KERNEL, "%d", id);
> + if (!name)
> + return NULL;
> +
> + group_kobj = kset_find_obj(iommu_group_kset, name);
> + kfree(name);
> +
> + if (!group_kobj)
> + return NULL;
> +
> + grp = container_of(group_kobj, struct iommu_group, kobj);
> + BUG_ON(grp->id != id);
> +
> + return grp;
> +}
> +EXPORT_SYMBOL_GPL(iommu_group_find);
Don't you need to do some reference counting here? Otherwise there's no
guarantee the returned pointer is still valid by the time it's used.
The interface should probably be iommu_group_get_by_id(). Thanks,
Alex
> +
> /**
> * iommu_group_get_iommudata - retrieve iommu_data registered for a group
> * @group: the group
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index f3b99e1..20281d5 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -113,6 +113,7 @@ struct iommu_ops {
> extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops);
> extern bool iommu_present(struct bus_type *bus);
> extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus);
> +extern struct iommu_group *iommu_group_find(int id);
> extern void iommu_domain_free(struct iommu_domain *domain);
> extern int iommu_attach_device(struct iommu_domain *domain,
> struct device *dev);
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