[PATCH 01/10] iommu: Remove useless group refcounting

[Jason Gunthorpe]

On Fri, Jul 21, 2023 at 07:10:57AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg at nvidia.com>
> > Sent: Wednesday, July 19, 2023 3:06 AM
> >
> >  int iommu_device_use_default_domain(struct device *dev)
> >  {
> > -	struct iommu_group *group = iommu_group_get(dev);
> > +	/* Caller must be a probed driver on dev */
> > +	struct iommu_group *group = dev->iommu_group;
> >  	int ret = 0;
> 
> this is called in the probing path by .dma_configure().
> 
> the driver hasn't been probed yet hence the rationale to not
> refcount is due to device_lock() instead?

At this point the driver core has partially attached/detached a driver
so I'm considering it part of the probed driver explanation.

Really during anything protected by the driver core probe path is
assured that the group cannot change.

Jason