Re: [RFC PATCH v10 0/5] fix vt-d hard lockup when hotplug ATS capable device

[Ethan Zhao <haifeng.zhao@linux.intel.com>]

On 1/18/2024 10:26 AM, Ethan Zhao wrote:
>
> On 1/18/2024 8:46 AM, Baolu Lu wrote:
>> On 1/17/24 5:00 PM, Ethan Zhao wrote:
>>> +       /*
>>> +        * If the ATS invalidation target device is gone this moment 
>>> (surprise
>>> +        * removed, died, no response) don't try this request again. 
>>> this
>>> +        * request will not get valid result anymore. but the 
>>> request was
>>> +        * already submitted to hardware and we predict to get a ITE in
>>> +        * followed batch of request, if so, it will get handled then.
>>> +        */
>>> +       if (target_pdev && !pci_device_is_present(target_pdev))
>>> +               return -EINVAL;
>>
>> Again, we should not ignore the error triggered by the current request.
>> Do not leave it to the next one. The WAIT descriptor is a fence. Handle
>> everything within its boundary.
>
>  We didn't set fence bit to every ATS invalidation wait descriptor,
>
> only the intel_drain_pasid_prq() queue a drain page requests with FN
>
> sit, but that is not called in hotplug removal path.

So, in fact so far, it doesn't act as a fence except the 
intel_drain_pasid_prq() ,

and it never handle everthing within its border.


Thanks,

Ethan

>
>
> Thanks,
>
> Ethan
>
>
>
>>
>> Best regards,
>> baolu
>