Re: [PATCH v1 1/5] iommufd: Create access in vfio_iommufd_emulated_bind()

[Nicolin Chen <nicolinc@nvidia.com>]

On Thu, Mar 16, 2023 at 12:17:11AM +0000, Tian, Kevin wrote:

> > > > > > > > @@ -449,33 +450,18 @@ iommufd_access_create(struct
> > > > iommufd_ctx

> > > > > > > >       refcount_inc(&access->obj.users);
> > > > > > > > +     mutex_init(&access->ioas_lock);
> > > > > > > >       access->ictx = ictx;
> > > > > > > >       iommufd_ctx_get(ictx);
> > > > > > >
> > > > > > > this refcnt get should be moved to the start given next patch
> > > > > > > removes the reference in the caller side.
> >
> > This change is ok but seems not necessary.
> >
> > Yes, vfio_iommufd_emulated_bind() will not have reference on the
> > ictx after the next patch. However, it gets reference only because it
> > wants to store it in vfio_device. Now, it does not store it. So no get.
> > I think the caller of vfio_iommufd_emulated_bind() should ensure
> > the ictx is valid. Also check the physical device bind. So maybe not
> > necessary to get ictx before calling iommufd_access_create(). This is
> > the same with the vfio_iommufd_physical_bind() which calls
> > iommufd_device_bind() without ictx get, and iommufd_device_bind()
> > also gets ictx in the end.
> >
> 
> You are right. I overlooked the fact that ictx is already held by the
> caller of bind.

I am dropping it then :)

Nic