On Mon, Jun 16, 2025 at 10:37:19AM -0300, Jason Gunthorpe wrote:
> On Sat, Jun 14, 2025 at 12:14:32AM -0700, Nicolin Chen wrote:
> > Now, access->ops can be NULL, to support an internal use case for the new
> > HW queue object. Since an access object in this case will be allocated by
> > an inernal iommufd object, the refcount on the ictx should be skipped, so
> > as not to deadlock the release of the ictx as it would otherwise wait for
> > the release of the access first during the release of the internal object
> > that could wait for the release of ictx:
> > ictx --releases--> hw_queue --releases--> access
> > ^ |
> > |_________________releases________________v
> >
> > Add a set of lightweight internal APIs to unlink access and ictx:
> > ictx --releases--> hw_queue --releases--> access
> >
> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > ---
> > drivers/iommu/iommufd/iommufd_private.h | 8 ++++
> > drivers/iommu/iommufd/device.c | 59 +++++++++++++++++++++----
> > 2 files changed, 58 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> > index 4a375a8c9216..468717d5e5bc 100644
> > --- a/drivers/iommu/iommufd/iommufd_private.h
> > +++ b/drivers/iommu/iommufd/iommufd_private.h
> > @@ -484,6 +484,14 @@ void iopt_remove_access(struct io_pagetable *iopt,
> > struct iommufd_access *access, u32 iopt_access_list_id);
> > void iommufd_access_destroy_object(struct iommufd_object *obj);
> >
> > +/* iommufd_access for internal use */
> > +struct iommufd_access *iommufd_access_create_internal(struct iommufd_ctx *ictx);
> > +#define iommufd_access_destroy_internal(ictx, access) \
> > + iommufd_object_destroy_user(ictx, &(access)->obj)
>
> Use a static inline please
>
> > +int iommufd_access_attach_internal(struct iommufd_access *access,
> > + struct iommufd_ioas *ioas);
> > +#define iommufd_access_detach_internal(access) iommufd_access_detach(access)
>
>
> > struct iommufd_eventq {
> > struct iommufd_object obj;
> > struct iommufd_ctx *ictx;
> > diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> > index 9293722b9cff..ad33f1e41a24 100644
> > --- a/drivers/iommu/iommufd/device.c
> > +++ b/drivers/iommu/iommufd/device.c
> > @@ -1084,7 +1084,39 @@ void iommufd_access_destroy_object(struct iommufd_object *obj)
> > if (access->ioas)
> > WARN_ON(iommufd_access_change_ioas(access, NULL));
> > mutex_unlock(&access->ioas_lock);
> > - iommufd_ctx_put(access->ictx);
> > + if (access->ops)
> > + iommufd_ctx_put(access->ictx);
>
> I was hoping we could null the ictx to signal internal? That didn't
> work out?
access->ictx should be NULL for internal. It should have been:
+ if (access->ictx)
+ iommufd_ctx_put(access->ictx);
> I would at least add a comment here this is filtering internal that
> doesn't have ictx. Maybe a little inline 'iommufd_access_is_internal'
> is appropriate. We'll be sad down the road if we need ops for
> internal.
Yea, an inline will be cleaner. Will add that.
Thanks
Nicolin
