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

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Date: Thu, 18 Jan 2024 10:26:14 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, kevin.tian@...el.com,
 bhelgaas@...gle.com, dwmw2@...radead.org, will@...nel.org,
 robin.murphy@....com, lukas@...ner.de
Cc: linux-pci@...r.kernel.org, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v10 0/5] fix vt-d hard lockup when hotplug ATS capable
 device


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.


Thanks,

Ethan



>
> Best regards,
> baolu