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SubjectRe: [PATCH v13 4/8] iommu/vt-d: Add bind guest PASID support
> +	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;

> + 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?

> + /*
> + * PASID table is per device for better security. Therefore, for
> + * each bind of a new device even with an existing PASID, we need to
> + * call the nested mode setup function here.
> + */
> + spin_lock(&iommu->lock);
> + ret = intel_pasid_setup_nested(iommu,
> + dev,
> + (pgd_t *)data->gpgd,
> + data->hpasid,
> + &data->vtd,
> + dmar_domain,
> + data->addr_width);

Why not:

et = intel_pasid_setup_nested(iommu, dev, (pgd_t *)data->gpgd,
data->hpasid, &data->vtd, dmar_domain,
data->addr_width);

?

> + for_each_svm_dev(sdev, svm, dev) {
> + ret = 0;

...

> + break;
> + }

Same only looks at the first device style. Why dos it only care about
the first device? That needs at least a comment, and probably a
first_svm_dev or so heper to make it explicit.

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