Re: [PATCH v10 08/12] iommu/sva: Refactoring iommu_sva_bind/unbind_device()

[Baolu Lu]

Hi Jean,

On 2022/7/25 15:39, Jean-Philippe Brucker wrote:
> On Sun, Jul 24, 2022 at 09:48:15PM +0800, Baolu Lu wrote:
> > /*
> >   * iommu_detach_device_pasid() - Detach the domain from pasid of device
> >   * @domain: the iommu domain.
> >   * @dev: the attached device.
> >   * @pasid: the pasid of the device.
> >   *
> >   * The @domain must have been attached to @pasid of the @dev with
> >   * iommu_detach_device_pasid().
> >   */
> > void iommu_detach_device_pasid(struct iommu_domain *domain, struct device
> > *dev,
> > 			       ioasid_t pasid)
> > {
> > 	struct iommu_group *group = iommu_group_get(dev);
> > 	struct group_pasid *param;
> >
> > 	mutex_lock(&group->mutex);
> > 	domain->ops->set_dev_pasid(group->blocking_domain, dev, pasid);
> Please also pass the old domain to this detach() function, so that the
> IOMMU driver doesn't have to keep track of them internally.

The iommu core provides the interface to retrieve attached domain with a
{device, pasid} pair. Therefore in the smmuv3 driver, the set_dev_pasid
could do like this:

+static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
+                                     struct device *dev, ioasid_t id)
+{
+       int ret = 0;
+       struct mm_struct *mm;
+       struct iommu_sva *handle;
+
+       /*
+        * Detach the domain if a blocking domain is set. Check the
+        * right domain type once the IOMMU driver supports a real
+        * blocking domain.
+        */
+       if (!domain || domain->type == IOMMU_DOMAIN_UNMANAGED) {
+               struct pasid_iommu *param;
+
+               param = iommu_device_pasid_param(dev, id);
+               if (!param || !param->domain)
+                       return -EINVAL;
+               arm_smmu_sva_block_dev_pasid(param->domain, dev, id);
+
+               return 0;
+       }
+
+       mm = domain->mm;
+       mutex_lock(&sva_lock);
+       handle = __arm_smmu_sva_bind(dev, mm);
+       if (IS_ERR(handle))
+               ret = PTR_ERR(handle);
+       mutex_unlock(&sva_lock);
+
+       return ret;
+}

The check of "(!domain || domain->type == IOMMU_DOMAIN_UNMANAGED)" looks
odd, but could get cleaned up after a real blocking domain is added.
Then, we can simply check "domain->type == IOMMU_DOMAIN_BLOCKING".

> In addition to clearing contexts, detach() also needs to invalidate TLBs,
> and for that the SMMU driver needs to know the old ASID (!= PASID) that
> was used by the context descriptor.

Best regards,
baolu