Re: [PATCH v8 12/12] iommu: Use refcount for fault data access

[Baolu Lu]

On 12/11/23 11:24 PM, Jason Gunthorpe wrote:
> Also iopf_queue_remove_device() is messed up - it returns an error
> code but nothing ever does anything with it 🙁 Remove functions like
> this should never fail.

Yes, agreed.

> Removal should be like I explained earlier:
>   - Disable new PRI reception

This could be done by

	rcu_assign_pointer(param->fault_param, NULL);

?

>   - Ack all outstanding PRQ to the device

All outstanding page requests are responded with
IOMMU_PAGE_RESP_INVALID, indicating that device should not attempt any
retry.

>   - Disable PRI on the device
>   - Tear down the iopf infrastructure
>
> So under this model if the iopf_queue_remove_device() has been called
> it should be sort of a 'disassociate' action where fault_param is
> still floating out there but iommu_page_response() does nothing.

Yes. All pending requests have been auto-responded.

> IOW pass the refcount from the iommu_report_device_fault() down into
> the fault handler, into the work and then into iommu_page_response()
> which will ultimately put it back.

Yes.

Best regards,
baolu