Re: [PATCH 1/2] iommu: Consolidate pasid dma ownership check

[Baolu Lu]

On 2023/8/1 15:03, Tian, Kevin wrote:
> >   /**
> >    * iommu_device_use_default_domain() - Device driver wants to handle
> > device
> >    *                                     DMA through the kernel DMA API.
> > @@ -3052,14 +3063,14 @@ int iommu_device_use_default_domain(struct
> > device *dev)
> >
> >   	mutex_lock(&group->mutex);
> >   	if (group->owner_cnt) {
> > -		if (group->owner || !iommu_is_default_domain(group) ||
> > -		    !xa_empty(&group->pasid_array)) {
> > +		if (group->owner || !iommu_is_default_domain(group)) {
> >   			ret = -EBUSY;
> >   			goto unlock_out;
> >   		}
> >   	}
> >
> >   	group->owner_cnt++;
> > +	assert_pasid_dma_ownership(group);
> Old code returns error if pasid_xrrary is not empty.
>
> New code continues to take ownership with a warning.
>
> this is a functional change. Is it intended or not?

If iommu_device_use_default_domain() is called with pasid_array not
empty, there must be a bug somewhere in the device driver. We should
WARN it instead of returning an error. Probably this is a functional
change? If so, I can add this in the commit message.

Best regards,
baolu