Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH v10 5/7] iommu/vt-d: Make prq draining code generic | Date | Wed, 19 Jul 2023 05:39:30 +0000 |
| |
> From: Baolu Lu <baolu.lu@linux.intel.com> > Sent: Friday, July 14, 2023 1:47 PM > > On 2023/7/14 11:49, Tian, Kevin wrote: > >> From: Baolu Lu <baolu.lu@linux.intel.com> > >> Sent: Friday, July 14, 2023 11:28 AM > >> > >> On 2023/7/13 15:49, Tian, Kevin wrote: > >>>> From: Jacob Pan <jacob.jun.pan@linux.intel.com> > >>>> Sent: Thursday, July 13, 2023 12:34 AM > >>>> > >>>> - /* Domain type specific cleanup: */ > >>>> domain = iommu_get_domain_for_dev_pasid(dev, pasid, 0); > >>>> - if (domain) { > >>>> - switch (domain->type) { > >>>> - case IOMMU_DOMAIN_SVA: > >>>> - intel_svm_remove_dev_pasid(dev, pasid); > >>>> - break; > >>>> - default: > >>>> - /* should never reach here */ > >>>> - WARN_ON(1); > >>>> - break; > >>>> - } > >>>> + if (!domain) > >>>> + goto out_tear_down; > >>> > >>> WARN_ON() > >> > >> Why? > >> > >> My understanding is that remve_device_pasid could be call in any context > >> including no domain attached. > >> > > > > oh I'm not aware of that. Can you elaborate the usage which uses a pasid > > w/o domain? pasid needs to point to a page table. Presumably every > > page table should be wrapped by a iommu domain... > > A case I can think of is error rewinding. A domain is being attached to > multiple pasids. When one of them is failed, remove_device_pasid should > be called on all pasids so that they are parked at a determinant state.
Can you elaborate what is the association among those pasid's so failing one would lead to failing all?
Just like a domain can be attached to multiple devices. I don't think there is an unwinding policy forcing to detach all devices just because there is a failure attaching the domain to a new one.
> > On the other hand, I don't want the remove_device_pasid to be the > counterpart of attach_dev_pasid. remove_device_pasid simply denotes: > > - The pasid will be parked in blocking state; > - If any domain that has been attached to this pasid, stop reference to > it any more. Otherwise, there might be use-after-free issues. > > Hence, remove_device_pasid should never fail. >
It should never fail. But could warn if there is a condition which shouldn't be hit. 😊
| |