Messages in this thread | | | Subject | Re: [PATCH] iommu: add a function to find an iommu group by id | From | Alex Williamson <> | Date | Fri, 22 Mar 2013 10:07:42 -0600 |
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On Fri, 2013-03-22 at 17:49 +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_get_by_id(id) function which performs > such search. > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > ---
v2: <describe what changed>
> drivers/iommu/iommu.c | 28 ++++++++++++++++++++++++++++ > include/linux/iommu.h | 1 + > 2 files changed, 29 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 1065a1a..531cbb5 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -204,6 +204,34 @@ again: > } > EXPORT_SYMBOL_GPL(iommu_group_alloc); > > +struct iommu_group *iommu_group_get_by_id(int id) > +{ > + struct kobject *group_kobj; > + struct iommu_group *grp;
This is named "group" everywhere else in this file.
> + 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);
This does a kobject_get on group->kobj
> + kfree(name); > + > + if (!group_kobj) > + return NULL; > + > + grp = container_of(group_kobj, struct iommu_group, kobj); > + BUG_ON(grp->id != id); > +
Here you want to exchange one reference for another, so first do the get:
> + kobject_get(grp->devices_kobj);
Now you need to release the get from the find:
kobject_put(&group->kobj)
> + > + return grp; > +} > +EXPORT_SYMBOL_GPL(iommu_group_get_by_id); > + > /** > * 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..00e5d7d 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_get_by_id(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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