linux-kernel - Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

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Date:   Tue, 8 Oct 2019 10:27:57 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Janusz Krzysztofik <janusz.krzysztofik@...ux.intel.com>
Cc:     baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Michał Wajdeczko <michal.wajdeczko@...el.com>
Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device
 hot re-plug

Hi,

On 10/1/19 11:01 PM, Janusz Krzysztofik wrote:
> Hi Baolu,
> 
> On Tuesday, September 3, 2019 9:41:23 AM CEST Janusz Krzysztofik wrote:
>> Hi Baolu,
>>
>> On Tuesday, September 3, 2019 3:29:40 AM CEST Lu Baolu wrote:
>>> Hi Janusz,
>>>
>>> On 9/2/19 4:37 PM, Janusz Krzysztofik wrote:
>>>>> I am not saying that keeping data is not acceptable. I just want to
>>>>> check whether there are any other solutions.
>>>> Then reverting 458b7c8e0dde and applying this patch still resolves the
>> issue
>>>> for me.  No errors appear when mappings are unmapped on device close after
>> the
>>>> device has been removed, and domain info preserved on device removal is
>>>> successfully reused on device re-plug.
>>>
>>> This patch doesn't look good to me although I agree that keeping data is
>>> acceptable.
> 
> Any progress with that?  Which mailing list should I watch for updates?\

We had a holiday last week. I will go ahead with reproducing it locally.
Feel free to let me know if you have any new proposal.

Best regards,
Baolu

> 
> Thanks,
> Janusz
> 
>>> It updates dev->archdata.iommu, but leaves the hardware
>>> context/pasid table unchanged. This might cause problems somewhere.
>>>
>>>>
>>>> Is there anything else I can do to help?
>>>
>>> Can you please tell me how to reproduce the problem?
>>
>> The most simple way to reproduce the issue, assuming there are no non-Intel
>> graphics adapters installed, is to run the following shell commands:
>>
>> #!/bin/sh
>> # load i915 module
>> modprobe i915
>> # open an i915 device and keep it open in background
>> cat /dev/dri/card0 >/dev/null &
>> sleep 2
>> # simulate device unplug
>> echo 1 >/sys/class/drm/card0/device/remove
>> # make the background process close the device on exit
>> kill $!
>>
>> Thanks,
>> Janusz
>>
>>
>>> Keeping the per
>>> device domain info while device is unplugged is a bit dangerous because
>>> info->dev might be a wild pointer. We need to work out a clean fix.
>>>
>>>>
>>>> Thanks,
>>>> Janusz
>>>>
>>>
>>> Best regards,
>>> Baolu
>>>
>>
>>
>>
>>
>>
> 
> 
> 
> 
>