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

[Baolu Lu]

On 2023/8/2 9:39, Tian, Kevin wrote:
> > From: Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Tuesday, August 1, 2023 3:44 PM
> >
> > 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.
> IMHO we should WARN*and*  return an error.

Okay, fine to me. Will make this in the next version.

Best regards,
baolu