Re: [PATCH v6 13/18] iommu/vt-d: Handle reattach of the restored domain

[Baolu Lu <baolu.lu@linux.intel.com>]

On 10/30/26 06:34, Samiullah Khawaja wrote:
>>> diff --git a/drivers/iommu/intel/liveupdate.c b/drivers/iommu/intel/ 
>>> liveupdate.c
>>> index 36816d3651e6..665ebb81bd61 100644
>>> --- a/drivers/iommu/intel/liveupdate.c
>>> +++ b/drivers/iommu/intel/liveupdate.c
>>> @@ -394,6 +394,137 @@ void 
>>> intel_iommu_handle_drhd_restore_failure(struct intel_iommu *iommu)
>>>                iommu->name);
>>>  }
>>> +static void domain_detach_restored_iommu(struct dmar_domain *domain,
>>> +                     struct intel_iommu *iommu)
>>> +{
>>> +    struct iommu_domain_info *info;
>>> +
>>> +    guard(mutex)(&iommu->did_lock);
>>> +    info = xa_load(&domain->iommu_array, iommu->seq_id);
>>> +    if (--info->refcnt == 0) {
>>> +        xa_erase(&domain->iommu_array, iommu->seq_id);
>>> +        kfree(info);
>>> +    }
>>
>> This seems to be different from normal domain_detach_iommu(), which
>> looks like this,
>>
>>        if (--info->refcnt == 0) {
>>                ida_free(&iommu->domain_ida, info->did);
>>                xa_erase(&domain->iommu_array, iommu->seq_id);
>>                kfree(info);
>>        }
>>
>> why ida_free() is skipped in the restored path?
> 
> The restored device can be removed and probed again while the PASID and
> context entries stay intact. So the restored did is not freed in this
> path. Once the domain is reclaimed by the iommufd, then it takes the
> normal detach path.

Can you please add a comment to explain this?

Thanks,
baolu