RE: [RFC 06/20] iommu: Add iommu_device_init[exit]_user_dma interfaces

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Monday, September 27, 2021 7:34 PM
> 
> On 2021/9/27 17:42, Tian, Kevin wrote:
> > +int iommu_device_set_dma_hint(struct device *dev, enum dma_hint hint)
> > +{
> > +	struct iommu_group *group;
> > +	int ret;
> > +
> > +	group = iommu_group_get(dev);
> > +	/* not an iommu-probed device */
> > +	if (!group)
> > +		return 0;
> > +
> > +	mutex_lock(&group->mutex);
> > +	ret = __iommu_group_viable(group, hint);
> > +	mutex_unlock(&group->mutex);
> > +
> > +	iommu_group_put(group);
> > +	return ret;
> > +}
> 
> Conceptually, we could also move iommu_deferred_attach() from
> iommu_dma_ops here to save unnecessary checks in the hot DMA API
> paths?
> 

Yes, it's possible. But just be curious, why doesn't iommu core 
manage deferred_attach when receiving BOUND_DRIVER event?
Is there other implication that deferred attach cannot be done
at driver binding time?

Thanks
Kevin