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Message-ID: <f6e57309-be5a-4a84-a280-6ed00a550548@linux.intel.com>
Date: Thu, 18 Jan 2024 10:32:20 +0800
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Subject: Re: [RFC PATCH v10 0/5] fix vt-d hard lockup when hotplug ATS capable
 device
From: Ethan Zhao <haifeng.zhao@linux.intel.com>
To: Baolu Lu <baolu.lu@linux.intel.com>, kevin.tian@intel.com,
 bhelgaas@google.com, dwmw2@infradead.org, will@kernel.org,
 robin.murphy@arm.com, lukas@wunner.de
Cc: linux-pci@vger.kernel.org, iommu@lists.linux.dev,
 linux-kernel@vger.kernel.org
References: <20231228170206.720675-1-haifeng.zhao@linux.intel.com>
 <1a2a4069-c737-4a3c-a2f6-cce06823331b@linux.intel.com>
 <3ee904e9-8a93-4bd9-8df7-6294885589e4@linux.intel.com>
 <42f7848a-0262-4871-b5dc-0e87beebfd11@linux.intel.com>
 <dcd27bc8-5eca-41ae-bb86-fd8e657ccfed@linux.intel.com>
 <d72d0a12-f3a4-4b4d-8b3b-5e59937a21d3@linux.intel.com>
 <5a9c38ec-1dc2-40d3-99eb-02b87be660a6@linux.intel.com>
 <9cc2010f-269c-4d23-b284-6fe4162f8810@linux.intel.com>
In-Reply-To: <9cc2010f-269c-4d23-b284-6fe4162f8810@linux.intel.com>
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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
>