Re: [PATCH v13 4/8] iommu/vt-d: Add bind guest PASID support

[Lu Baolu]

Hi Jacob,

On 2020/5/14 23:57, Jacob Pan wrote:
> Hi Christoph,
>
> Thanks a lot for the reviews, comments below.
>
> Jacob
>
> On Wed, 13 May 2020 22:59:30 -0700
> Christoph Hellwig<hch@xxxxxxxxxxxxx>  wrote:
>
> > > +	if (dev_is_pci(dev)) {
> > > +		/* VT-d supports devices with full 20 bit PASIDs
> > > only */
> > > +		if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
> > > +			return -EINVAL;
> > > +	} else {
> > > +		return -ENOTSUPP;
> > > +	}
> > This looks strange.  Why not:
> >
> > 	if (!dev_is_pci(dev)) {
> > 		return -ENOTSUPP;
> >
> > 	/* VT-d supports devices with full 20 bit PASIDs only */
> > 	if (pci_max_pasids(to_pci_dev(dev)) != PASID_MAX)
> > 		return -EINVAL;
> That is better, will do.
>
> > > +		for_each_svm_dev(sdev, svm, dev) {
> > > +			/*
> > > +			 * For devices with aux domains, we should
> > > allow multiple
> > > +			 * bind calls with the same PASID and pdev.
> > > +			 */
> > > +			if (iommu_dev_feature_enabled(dev,
> > > IOMMU_DEV_FEAT_AUX)) {
> > > +				sdev->users++;
> > > +			} else {
> > > +				dev_warn_ratelimited(dev, "Already
> > > bound with PASID %u\n",
> > > +						svm->pasid);
> > > +				ret = -EBUSY;
> > > +			}
> > > +			goto out;
> > Is this intentionally a for loop that jumps out of the loop after
> > the first device?
> The name is confusing, it is not a loop. I will change it to
> find_svm_dev() and comments like this?
>
> /*
>   * Find the matching device in a given SVM. The bind code ensures that
>   * each device can only be added to the SVM list once.
>   */
> #define find_svm_dev(sdev, svm, d)			\
> 	list_for_each_entry((sdev), &(svm)->devs, list)	\
> 		if ((d) != (sdev)->dev) {} else

The for_each_svm_dev() is not added by this series and is also used by
other functions. How about changing it in a separated patch?

Best regards,
baolu