Re: [PATCH v5 7/9] iommufd: Associate fault object with iommufd_hw_pgtable

Baolu Lu
2024-05-20T04:02:35Z

On 5/20/24 11:39 AM, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@linux.intel.com>
>> Sent: Monday, May 20, 2024 10:19 AM
>>
>> On 5/15/24 4:50 PM, Tian, Kevin wrote:
>>>> From: Lu Baolu <baolu.lu@linux.intel.com>
>>>> Sent: Tuesday, April 30, 2024 10:57 PM
>>>>
>>>> @@ -308,6 +314,19 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd
>>>> *ucmd)
>>>> goto out_put_pt;
>>>> }
>>>>
>>>> + if (cmd->flags & IOMMU_HWPT_FAULT_ID_VALID) {
>>>> + struct iommufd_fault *fault;
>>>> +
>>>> + fault = iommufd_get_fault(ucmd, cmd->fault_id);
>>>> + if (IS_ERR(fault)) {
>>>> + rc = PTR_ERR(fault);
>>>> + goto out_hwpt;
>>>> + }
>>>> + hwpt->fault = fault;
>>>> + hwpt->domain->iopf_handler = iommufd_fault_iopf_handler;
>>>> + hwpt->domain->fault_data = hwpt;
>>>> + }
>>>
>>> this is nesting specific. why not moving it to the nested_alloc()?
>>
>> Nesting is currently a use case for userspace I/O page faults, but this
>> design should be general enough to support other scenarios as well.
>>
>
> Do we allow user page table w/o nesting?
>
> What would be a scenario in which the user doesn't manage the
> page table but still want to handle the I/O page fault? The fault
> should always be delivered to the owner managing the page table...

I am not sure. But if nesting is the only case for user page table, it's
fine to move above code to the nested_alloc helper.

Best regards,
baolu