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

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

[Janusz Krzysztofik]

When a perfectly working i915 device is hot unplugged (via sysfs) and
hot re-plugged again, its dev->archdata.iommu field is not populated
again with an IOMMU pointer.  As a result, the device probe fails on
DMA mapping error during scratch page setup.

It looks like that happens because devices are not detached from their
MMUIO bus before they are removed on device unplug.  Then, when an
already registered device/IOMMU association is identified by the
reinstantiated device's bus and function IDs on IOMMU bus re-attach
attempt, the device's archdata is not populated with IOMMU information
and the bad happens.

I'm not sure if this is a proper fix but it works for me so at least it
confirms correctness of my analysis results, I believe.  So far I
haven't been able to identify a good place where the possibly missing
IOMMU bus detach on device unplug operation could be added.

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 12d094d08c0a..7cdcd0595408 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2477,6 +2477,9 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
 		if (info2) {
 			found      = info2->domain;
 			info2->dev = dev;
+
+			if (dev && !dev->archdata.iommu)
+				dev->archdata.iommu = info2;
 		}
 	}
 
-- 
2.21.0

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

[Lu Baolu]

Hi,

On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
> When a perfectly working i915 device is hot unplugged (via sysfs) and
> hot re-plugged again, its dev->archdata.iommu field is not populated
> again with an IOMMU pointer.  As a result, the device probe fails on
> DMA mapping error during scratch page setup.
> 
> It looks like that happens because devices are not detached from their
> MMUIO bus before they are removed on device unplug.  Then, when an
> already registered device/IOMMU association is identified by the
> reinstantiated device's bus and function IDs on IOMMU bus re-attach
> attempt, the device's archdata is not populated with IOMMU information
> and the bad happens.
> 
> I'm not sure if this is a proper fix but it works for me so at least it
> confirms correctness of my analysis results, I believe.  So far I
> haven't been able to identify a good place where the possibly missing
> IOMMU bus detach on device unplug operation could be added.

Which kernel version are you testing with? Does it contain below commit?

commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
Author: Lu Baolu <baolu.lu@linux.intel.com>
Date:   Thu Aug 1 11:14:58 2019 +0800

     iommu/vt-d: Detach domain when move device out of group

     When removing a device from an iommu group, the domain should
     be detached from the device. Otherwise, the stale domain info
     will still be cached by the driver and the driver will refuse
     to attach any domain to the device again.

     Cc: Ashok Raj <ashok.raj@intel.com>
     Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
     Cc: Kevin Tian <kevin.tian@intel.com>
     Fixes: b7297783c2bb6 ("iommu/vt-d: Remove duplicated code for 
device hotplug")
     Reported-and-tested-by: Vlad Buslov <vladbu@mellanox.com>
     Suggested-by: Robin Murphy <robin.murphy@arm.com>
     Link: https://lkml.org/lkml/2019/7/26/1133
     Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
     Signed-off-by: Joerg Roedel <jroedel@suse.de>

Best regards,
Lu Baolu

> 
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
> ---
>   drivers/iommu/intel-iommu.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 12d094d08c0a..7cdcd0595408 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2477,6 +2477,9 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
>   		if (info2) {
>   			found      = info2->domain;
>   			info2->dev = dev;
> +
> +			if (dev && !dev->archdata.iommu)
> +				dev->archdata.iommu = info2;
>   		}
>   	}
>   
> 
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Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Janusz Krzysztofik]

Hi Lu,

On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote:
> Hi,
> 
> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
> > When a perfectly working i915 device is hot unplugged (via sysfs) and
> > hot re-plugged again, its dev->archdata.iommu field is not populated
> > again with an IOMMU pointer.  As a result, the device probe fails on
> > DMA mapping error during scratch page setup.
> > 
> > It looks like that happens because devices are not detached from their
> > MMUIO bus before they are removed on device unplug.  Then, when an
> > already registered device/IOMMU association is identified by the
> > reinstantiated device's bus and function IDs on IOMMU bus re-attach
> > attempt, the device's archdata is not populated with IOMMU information
> > and the bad happens.
> > 
> > I'm not sure if this is a proper fix but it works for me so at least it
> > confirms correctness of my analysis results, I believe.  So far I
> > haven't been able to identify a good place where the possibly missing
> > IOMMU bus detach on device unplug operation could be added.
> 
> Which kernel version are you testing with? Does it contain below commit?
> 
> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
> Author: Lu Baolu <baolu.lu@linux.intel.com>
> Date:   Thu Aug 1 11:14:58 2019 +0800

I was using an internal branch based on drm-tip which didn't contain this 
commit yet.  Fortunately it has been already merged into drm-tip over last 
weekend and has effectively fixed the issue.

Thanks,
Janusz

>      iommu/vt-d: Detach domain when move device out of group
> 
>      When removing a device from an iommu group, the domain should
>      be detached from the device. Otherwise, the stale domain info
>      will still be cached by the driver and the driver will refuse
>      to attach any domain to the device again.
> 
>      Cc: Ashok Raj <ashok.raj@intel.com>
>      Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>      Cc: Kevin Tian <kevin.tian@intel.com>
>      Fixes: b7297783c2bb6 ("iommu/vt-d: Remove duplicated code for 
> device hotplug")
>      Reported-and-tested-by: Vlad Buslov <vladbu@mellanox.com>
>      Suggested-by: Robin Murphy <robin.murphy@arm.com>
>      Link: https://lkml.org/lkml/2019/7/26/1133
>      Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>      Signed-off-by: Joerg Roedel <jroedel@suse.de>
> 
> Best regards,
> Lu Baolu
> 
> > 
> > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
> > ---
> >   drivers/iommu/intel-iommu.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index 12d094d08c0a..7cdcd0595408 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -2477,6 +2477,9 @@ static struct dmar_domain 
*dmar_insert_one_dev_info(struct intel_iommu *iommu,
> >   		if (info2) {
> >   			found      = info2->domain;
> >   			info2->dev = dev;
> > +
> > +			if (dev && !dev->archdata.iommu)
> > +				dev->archdata.iommu = info2;
> >   		}
> >   	}
> >   
> > 
> 




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

[Lu Baolu]

Hi Janusz,

On 8/26/19 4:15 PM, Janusz Krzysztofik wrote:
> Hi Lu,
> 
> On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote:
>> Hi,
>>
>> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
>>> When a perfectly working i915 device is hot unplugged (via sysfs) and
>>> hot re-plugged again, its dev->archdata.iommu field is not populated
>>> again with an IOMMU pointer.  As a result, the device probe fails on
>>> DMA mapping error during scratch page setup.
>>>
>>> It looks like that happens because devices are not detached from their
>>> MMUIO bus before they are removed on device unplug.  Then, when an
>>> already registered device/IOMMU association is identified by the
>>> reinstantiated device's bus and function IDs on IOMMU bus re-attach
>>> attempt, the device's archdata is not populated with IOMMU information
>>> and the bad happens.
>>>
>>> I'm not sure if this is a proper fix but it works for me so at least it
>>> confirms correctness of my analysis results, I believe.  So far I
>>> haven't been able to identify a good place where the possibly missing
>>> IOMMU bus detach on device unplug operation could be added.
>>
>> Which kernel version are you testing with? Does it contain below commit?
>>
>> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
>> Author: Lu Baolu <baolu.lu@linux.intel.com>
>> Date:   Thu Aug 1 11:14:58 2019 +0800
> 
> I was using an internal branch based on drm-tip which didn't contain this
> commit yet.  Fortunately it has been already merged into drm-tip over last
> weekend and has effectively fixed the issue.

Thanks for testing this.

Best regards,
Lu Baolu
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Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Janusz Krzysztofik]

Hi Lu,

On Monday, August 26, 2019 10:29:12 AM CEST Lu Baolu wrote:
> Hi Janusz,
> 
> On 8/26/19 4:15 PM, Janusz Krzysztofik wrote:
> > Hi Lu,
> > 
> > On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote:
> >> Hi,
> >>
> >> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
> >>> When a perfectly working i915 device is hot unplugged (via sysfs) and
> >>> hot re-plugged again, its dev->archdata.iommu field is not populated
> >>> again with an IOMMU pointer.  As a result, the device probe fails on
> >>> DMA mapping error during scratch page setup.
> >>>
> >>> It looks like that happens because devices are not detached from their
> >>> MMUIO bus before they are removed on device unplug.  Then, when an
> >>> already registered device/IOMMU association is identified by the
> >>> reinstantiated device's bus and function IDs on IOMMU bus re-attach
> >>> attempt, the device's archdata is not populated with IOMMU information
> >>> and the bad happens.
> >>>
> >>> I'm not sure if this is a proper fix but it works for me so at least it
> >>> confirms correctness of my analysis results, I believe.  So far I
> >>> haven't been able to identify a good place where the possibly missing
> >>> IOMMU bus detach on device unplug operation could be added.
> >>
> >> Which kernel version are you testing with? Does it contain below commit?
> >>
> >> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
> >> Author: Lu Baolu <baolu.lu@linux.intel.com>
> >> Date:   Thu Aug 1 11:14:58 2019 +0800
> > 
> > I was using an internal branch based on drm-tip which didn't contain this
> > commit yet.  Fortunately it has been already merged into drm-tip over last
> > weekend and has effectively fixed the issue.
> 
> Thanks for testing this.

My testing appeared not sufficiently exhaustive. The fix indeed resolved my 
initially discovered issue of not being able to rebind the i915 driver to a 
re-plugged device, however it brought another, probably more serious problem 
to light.

When an open i915 device is hot unplugged, IOMMU bus notifier now cleans up 
IOMMU info for the device on PCI device remove while the i915 driver is still 
not released, kept by open file descriptors.  Then, on last device close, 
cleanup attempts lead to kernel panic raised from intel_unmap() on unresolved 
IOMMU domain.

With commit 458b7c8e0dde reverted and my fix applied, both late device close 
and device re-plug work for me.  However, I can realize that's probably still 
not a complete solution, possibly missing some protection against reuse of a 
removed device other than for cleanup.  If you think that's the right way to 
go, I can work more on that.

I've had a look at other drivers and found AMD is using somehow similar 
approach.  On the other hand, looking at the IOMMU common code I couldn't 
identify any arrangement that would support deferred device cleanup.

If that approach is not acceptable for Intel IOMMU, please suggest a way you'd 
like to have it resolved and I can try to implement it.

Thanks,
Janusz

> Best regards,
> Lu Baolu
> 




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

[Lu Baolu]

Hi Janusz,

On 8/27/19 5:35 PM, Janusz Krzysztofik wrote:
> Hi Lu,
> 
> On Monday, August 26, 2019 10:29:12 AM CEST Lu Baolu wrote:
>> Hi Janusz,
>>
>> On 8/26/19 4:15 PM, Janusz Krzysztofik wrote:
>>> Hi Lu,
>>>
>>> On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote:
>>>> Hi,
>>>>
>>>> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
>>>>> When a perfectly working i915 device is hot unplugged (via sysfs) and
>>>>> hot re-plugged again, its dev->archdata.iommu field is not populated
>>>>> again with an IOMMU pointer.  As a result, the device probe fails on
>>>>> DMA mapping error during scratch page setup.
>>>>>
>>>>> It looks like that happens because devices are not detached from their
>>>>> MMUIO bus before they are removed on device unplug.  Then, when an
>>>>> already registered device/IOMMU association is identified by the
>>>>> reinstantiated device's bus and function IDs on IOMMU bus re-attach
>>>>> attempt, the device's archdata is not populated with IOMMU information
>>>>> and the bad happens.
>>>>>
>>>>> I'm not sure if this is a proper fix but it works for me so at least it
>>>>> confirms correctness of my analysis results, I believe.  So far I
>>>>> haven't been able to identify a good place where the possibly missing
>>>>> IOMMU bus detach on device unplug operation could be added.
>>>>
>>>> Which kernel version are you testing with? Does it contain below commit?
>>>>
>>>> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
>>>> Author: Lu Baolu <baolu.lu@linux.intel.com>
>>>> Date:   Thu Aug 1 11:14:58 2019 +0800
>>>
>>> I was using an internal branch based on drm-tip which didn't contain this
>>> commit yet.  Fortunately it has been already merged into drm-tip over last
>>> weekend and has effectively fixed the issue.
>>
>> Thanks for testing this.
> 
> My testing appeared not sufficiently exhaustive. The fix indeed resolved my
> initially discovered issue of not being able to rebind the i915 driver to a
> re-plugged device, however it brought another, probably more serious problem
> to light.
> 
> When an open i915 device is hot unplugged, IOMMU bus notifier now cleans up
> IOMMU info for the device on PCI device remove while the i915 driver is still
> not released, kept by open file descriptors.  Then, on last device close,
> cleanup attempts lead to kernel panic raised from intel_unmap() on unresolved
> IOMMU domain.

We should avoid kernel panic when a intel_unmap() is called against
a non-existent domain. But we shouldn't expect the IOMMU driver not
cleaning up the domain info when a device remove notification comes and 
wait until all file descriptors being closed, right?

Best regards,
Baolu

> 
> With commit 458b7c8e0dde reverted and my fix applied, both late device close
> and device re-plug work for me.  However, I can realize that's probably still
> not a complete solution, possibly missing some protection against reuse of a
> removed device other than for cleanup.  If you think that's the right way to
> go, I can work more on that.
> 
> I've had a look at other drivers and found AMD is using somehow similar
> approach.  On the other hand, looking at the IOMMU common code I couldn't
> identify any arrangement that would support deferred device cleanup.
> 
> If that approach is not acceptable for Intel IOMMU, please suggest a way you'd
> like to have it resolved and I can try to implement it.
> 
> Thanks,
> Janusz
> 
>> Best regards,
>> Lu Baolu
>>
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Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Janusz Krzysztofik]

On Wednesday, August 28, 2019 2:56:18 AM CEST Lu Baolu wrote:
> Hi Janusz,
> 
> On 8/27/19 5:35 PM, Janusz Krzysztofik wrote:
> > Hi Lu,
> > 
> > On Monday, August 26, 2019 10:29:12 AM CEST Lu Baolu wrote:
> >> Hi Janusz,
> >>
> >> On 8/26/19 4:15 PM, Janusz Krzysztofik wrote:
> >>> Hi Lu,
> >>>
> >>> On Friday, August 23, 2019 3:51:11 AM CEST Lu Baolu wrote:
> >>>> Hi,
> >>>>
> >>>> On 8/22/19 10:29 PM, Janusz Krzysztofik wrote:
> >>>>> When a perfectly working i915 device is hot unplugged (via sysfs) and
> >>>>> hot re-plugged again, its dev->archdata.iommu field is not populated
> >>>>> again with an IOMMU pointer.  As a result, the device probe fails on
> >>>>> DMA mapping error during scratch page setup.
> >>>>>
> >>>>> It looks like that happens because devices are not detached from their
> >>>>> MMUIO bus before they are removed on device unplug.  Then, when an
> >>>>> already registered device/IOMMU association is identified by the
> >>>>> reinstantiated device's bus and function IDs on IOMMU bus re-attach
> >>>>> attempt, the device's archdata is not populated with IOMMU information
> >>>>> and the bad happens.
> >>>>>
> >>>>> I'm not sure if this is a proper fix but it works for me so at least 
it
> >>>>> confirms correctness of my analysis results, I believe.  So far I
> >>>>> haven't been able to identify a good place where the possibly missing
> >>>>> IOMMU bus detach on device unplug operation could be added.
> >>>>
> >>>> Which kernel version are you testing with? Does it contain below 
commit?
> >>>>
> >>>> commit 458b7c8e0dde12d140e3472b80919cbb9ae793f4
> >>>> Author: Lu Baolu <baolu.lu@linux.intel.com>
> >>>> Date:   Thu Aug 1 11:14:58 2019 +0800
> >>>
> >>> I was using an internal branch based on drm-tip which didn't contain 
this
> >>> commit yet.  Fortunately it has been already merged into drm-tip over 
last
> >>> weekend and has effectively fixed the issue.
> >>
> >> Thanks for testing this.
> > 
> > My testing appeared not sufficiently exhaustive. The fix indeed resolved 
my
> > initially discovered issue of not being able to rebind the i915 driver to 
a
> > re-plugged device, however it brought another, probably more serious 
problem
> > to light.
> > 
> > When an open i915 device is hot unplugged, IOMMU bus notifier now cleans 
up
> > IOMMU info for the device on PCI device remove while the i915 driver is 
still
> > not released, kept by open file descriptors.  Then, on last device close,
> > cleanup attempts lead to kernel panic raised from intel_unmap() on 
unresolved
> > IOMMU domain.
> 
> We should avoid kernel panic when a intel_unmap() is called against
> a non-existent domain.

Does that mean you suggest to replace
	BUG_ON(!domain);
with something like
	if (WARN_ON(!domain))
		return;
and to not care of orphaned mappings left allocated?  Is there a way to inform 
users that their active DMA mappings are no longer valid and they shouldn't 
call dma_unmap_*()?

> But we shouldn't expect the IOMMU driver not
> cleaning up the domain info when a device remove notification comes and 
> wait until all file descriptors being closed, right?

Shouldn't then the IOMMU driver take care of cleaning up resources still 
allocated on device remove before it invalidates and forgets their pointers?

Thanks,
Janusz


> Best regards,
> Baolu
> 
> > 
> > With commit 458b7c8e0dde reverted and my fix applied, both late device 
close
> > and device re-plug work for me.  However, I can realize that's probably 
still
> > not a complete solution, possibly missing some protection against reuse of 
a
> > removed device other than for cleanup.  If you think that's the right way 
to
> > go, I can work more on that.
> > 
> > I've had a look at other drivers and found AMD is using somehow similar
> > approach.  On the other hand, looking at the IOMMU common code I couldn't
> > identify any arrangement that would support deferred device cleanup.
> > 
> > If that approach is not acceptable for Intel IOMMU, please suggest a way 
you'd
> > like to have it resolved and I can try to implement it.
> > 
> > Thanks,
> > Janusz
> > 
> >> Best regards,
> >> Lu Baolu
> >>
> 




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

[Lu Baolu]

Hi Janusz,

On 8/28/19 10:17 PM, Janusz Krzysztofik wrote:
>> We should avoid kernel panic when a intel_unmap() is called against
>> a non-existent domain.
> Does that mean you suggest to replace
> 	BUG_ON(!domain);
> with something like
> 	if (WARN_ON(!domain))
> 		return;
> and to not care of orphaned mappings left allocated?  Is there a way to inform
> users that their active DMA mappings are no longer valid and they shouldn't
> call dma_unmap_*()?
> 
>> But we shouldn't expect the IOMMU driver not
>> cleaning up the domain info when a device remove notification comes and
>> wait until all file descriptors being closed, right?
> Shouldn't then the IOMMU driver take care of cleaning up resources still
> allocated on device remove before it invalidates and forgets their pointers?
> 

You are right. We need to wait until all allocated resources (iova and
mappings) to be released.

How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and
removing the domain info when the driver detachment completes?

> Thanks,
> Janusz

Best regards,
Baolu
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Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Janusz Krzysztofik]

Hi Baolu,

On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote:
> Hi Janusz,
> 
> On 8/28/19 10:17 PM, Janusz Krzysztofik wrote:
> >> We should avoid kernel panic when a intel_unmap() is called against
> >> a non-existent domain.
> > Does that mean you suggest to replace
> > 	BUG_ON(!domain);
> > with something like
> > 	if (WARN_ON(!domain))
> > 		return;
> > and to not care of orphaned mappings left allocated?  Is there a way to 
inform
> > users that their active DMA mappings are no longer valid and they 
shouldn't
> > call dma_unmap_*()?
> > 
> >> But we shouldn't expect the IOMMU driver not
> >> cleaning up the domain info when a device remove notification comes and
> >> wait until all file descriptors being closed, right?
> > Shouldn't then the IOMMU driver take care of cleaning up resources still
> > allocated on device remove before it invalidates and forgets their 
pointers?
> > 
> 
> You are right. We need to wait until all allocated resources (iova and
> mappings) to be released.
> 
> How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and
> removing the domain info when the driver detachment completes?

Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, regardless 
of a device being removed or not.  As long as the device is not unplugged and 
the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound driver is 
not a problem here.
Morever, BUS_NOTIFY_UNBOUND_DRIVER  is called even before 
BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway.
Last but not least, bus events are independent of the IOMMU driver use via 
DMA-API it exposes.

If keeping data for unplugged devices and reusing it on device re-plug is not 
acceptable then maybe the IOMMU driver should perform reference counting of 
its internal resources occupied by DMA-API users and perform cleanups on last 
release?

Thanks,
Janusz


> > Thanks,
> > Janusz
> 
> Best regards,
> Baolu
> 




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

[Lu Baolu]

Hi,

On 8/29/19 3:58 PM, Janusz Krzysztofik wrote:
> Hi Baolu,
> 
> On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote:
>> Hi Janusz,
>>
>> On 8/28/19 10:17 PM, Janusz Krzysztofik wrote:
>>>> We should avoid kernel panic when a intel_unmap() is called against
>>>> a non-existent domain.
>>> Does that mean you suggest to replace
>>> 	BUG_ON(!domain);
>>> with something like
>>> 	if (WARN_ON(!domain))
>>> 		return;
>>> and to not care of orphaned mappings left allocated?  Is there a way to
> inform
>>> users that their active DMA mappings are no longer valid and they
> shouldn't
>>> call dma_unmap_*()?
>>>
>>>> But we shouldn't expect the IOMMU driver not
>>>> cleaning up the domain info when a device remove notification comes and
>>>> wait until all file descriptors being closed, right?
>>> Shouldn't then the IOMMU driver take care of cleaning up resources still
>>> allocated on device remove before it invalidates and forgets their
> pointers?
>>>
>>
>> You are right. We need to wait until all allocated resources (iova and
>> mappings) to be released.
>>
>> How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and
>> removing the domain info when the driver detachment completes?
> 
> Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, regardless
> of a device being removed or not.  As long as the device is not unplugged and
> the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound driver is
> not a problem here.
> Morever, BUS_NOTIFY_UNBOUND_DRIVER  is called even before
> BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway.
> Last but not least, bus events are independent of the IOMMU driver use via
> DMA-API it exposes.

Fair enough.

> 
> If keeping data for unplugged devices and reusing it on device re-plug is not
> acceptable then maybe the IOMMU driver should perform reference counting of
> its internal resources occupied by DMA-API users and perform cleanups on last
> release?

I am not saying that keeping data is not acceptable. I just want to
check whether there are any other solutions.

Best regards,
Baolu
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Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Janusz Krzysztofik]

Hi Baolu,

On Thursday, August 29, 2019 11:08:18 AM CEST Lu Baolu wrote:
> Hi,
> 
> On 8/29/19 3:58 PM, Janusz Krzysztofik wrote:
> > Hi Baolu,
> > 
> > On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote:
> >> Hi Janusz,
> >>
> >> On 8/28/19 10:17 PM, Janusz Krzysztofik wrote:
> >>>> We should avoid kernel panic when a intel_unmap() is called against
> >>>> a non-existent domain.
> >>> Does that mean you suggest to replace
> >>> 	BUG_ON(!domain);
> >>> with something like
> >>> 	if (WARN_ON(!domain))
> >>> 		return;
> >>> and to not care of orphaned mappings left allocated?  Is there a way to
> > inform
> >>> users that their active DMA mappings are no longer valid and they
> > shouldn't
> >>> call dma_unmap_*()?
> >>>
> >>>> But we shouldn't expect the IOMMU driver not
> >>>> cleaning up the domain info when a device remove notification comes and
> >>>> wait until all file descriptors being closed, right?
> >>> Shouldn't then the IOMMU driver take care of cleaning up resources still
> >>> allocated on device remove before it invalidates and forgets their
> > pointers?
> >>>
> >>
> >> You are right. We need to wait until all allocated resources (iova and
> >> mappings) to be released.
> >>
> >> How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and
> >> removing the domain info when the driver detachment completes?
> > 
> > Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, 
regardless
> > of a device being removed or not.  As long as the device is not unplugged 
and
> > the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound 
driver is
> > not a problem here.
> > Morever, BUS_NOTIFY_UNBOUND_DRIVER  is called even before
> > BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway.
> > Last but not least, bus events are independent of the IOMMU driver use via
> > DMA-API it exposes.
> 
> Fair enough.
> 
> > 
> > If keeping data for unplugged devices and reusing it on device re-plug is 
not
> > acceptable then maybe the IOMMU driver should perform reference counting 
of
> > its internal resources occupied by DMA-API users and perform cleanups on 
last
> > release?
> 
> 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.

Is there anything else I can do to help?

Thanks,
Janusz

> 
> Best regards,
> Baolu
> 




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

[Lu Baolu]

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

[Janusz Krzysztofik]

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. 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
> 




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

[Janusz Krzysztofik]

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?

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
> > 
> 
> 
> 
> 
> 




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

[Lu Baolu]

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

[Lu Baolu]

Hi Janusz,

On 9/3/19 3:41 PM, 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. 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 $!
> 

I tried to reproduce the issue with above instructions. I got below
kernel messages after above operation. Is it the same as what you've
seen? I can't find anything explicitly related to iommu except an IOMMU
fault generated after device got removed and the DMA translation
structures got torn down. Can you please help me to understand how IOMMU
driver triggers the issue?


[  182.217672] ------------[ cut here ]------------
[  182.217679] WARNING: CPU: 1 PID: 1285 at 
drivers/gpu/drm/drm_mode_config.c:495 drm_mode_config_cleanup+0x2cb/0x2e0
[  182.217680] Modules linked in: nls_iso8859_1 snd_soc_skl 
snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core 
snd_soc_acpi_intel_match snd_soc_acpi snd_soc_core intel_rapl_msr 
snd_hda_codec_hdmi snd_hda_codec_realtek snd_compress 
snd_hda_codec_generic ledtrig_audio ac97_bus snd_pcm_dmaengine 
snd_hda_intel snd_intel_nhlt snd_hda_codec snd_hda_core snd_hwdep 
snd_pcm intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp 
kvm_intel kvm snd_seq_midi irqbypass snd_seq_midi_event snd_rawmidi 
crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iwlmvm snd_seq 
mac80211 libarc4 aesni_intel snd_seq_device snd_timer crypto_simd 
ipu3_cio2 cryptd glue_helper iwlwifi v4l2_fwnode intel_cstate 
videobuf2_dma_sg videobuf2_memops intel_rapl_perf asix videobuf2_v4l2 
videobuf2_common usbnet mii cfg80211 input_leds serio_raw 
intel_wmi_thunderbolt snd mei_me videodev soundcore 
intel_xhci_usb_role_switch mei 8250_dw mc roles intel_pch_thermal 
hid_sensor_magn_3d hid_sensor_accel_3d hid_sensor_press
[  182.217709]  hid_sensor_incl_3d hid_sensor_als hid_sensor_rotation 
hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer 
kfifo_buf hid_sensor_iio_common industrialio intel_vbtn mac_hid 
intel_hid acpi_pad sparse_keymap sch_fq_codel parport_pc ppdev lp 
parport ip_tables x_tables hid_sensor_custom hid_sensor_hub 
intel_ishtp_hid hid_generic dwc3 ulpi udc_core i2c_designware_platform 
i2c_designware_core e1000e psmouse i2c_i801 tg3 usbhid dwc3_pci hid 
intel_ish_ipc intel_lpss_pci intel_ishtp intel_lpss wmi 
pinctrl_sunrisepoint pinctrl_intel
[  182.217727] CPU: 1 PID: 1285 Comm: bash Not tainted 5.4.0-rc2+ #2704
[  182.217728] Hardware name: Intel Corporation Skylake Client 
platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B105.B00.1512051901 
12/05/2015
[  182.217731] RIP: 0010:drm_mode_config_cleanup+0x2cb/0x2e0
[  182.217732] Code: eb 0c 48 8b 70 48 4c 89 e7 e8 31 f4 ff ff 48 8d 7d 
a0 e8 d8 95 ff ff 48 85 c0 75 e6 48 8d 7d a0 e8 1a 87 ff ff e9 ef fd ff 
ff <0f> 0b e9 ed fe ff ff 0f 0b eb 98 e8 05 ec 98 ff 0f 1f 44 00 00 0f
[  182.217733] RSP: 0018:ffffa1c481d37c78 EFLAGS: 00010216
[  182.217735] RAX: ffff95c7da326e08 RBX: ffff95c7dcf60000 RCX: 
000000008010000e
[  182.217735] RDX: ffff95c7dcf603b8 RSI: 000000008010000e RDI: 
ffff95c7dcf60390
[  182.217736] RBP: ffffa1c481d37cd8 R08: 0000000000000000 R09: 
ffffffff9e035e00
[  182.217737] R10: ffffa1c481d37be0 R11: 0000000000000001 R12: 
ffff95c7dcf60250
[  182.217737] R13: ffff95c7dcf603b8 R14: ffffa1c481d37ee8 R15: 
fffffffffffffff2
[  182.217739] FS:  00007f804af7f740(0000) GS:ffff95c7e7a80000(0000) 
knlGS:0000000000000000
[  182.217739] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  182.217740] CR2: 00007ffebc530cec CR3: 0000000137e0e003 CR4: 
00000000003606e0
[  182.217741] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[  182.217742] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400
[  182.217742] Call Trace:
[  182.217748]  ? _cond_resched+0x19/0x40
[  182.217752]  intel_modeset_driver_remove+0xd1/0x150
[  182.217754]  i915_driver_remove+0xb8/0x120
[  182.217756]  i915_pci_remove+0x23/0x40
[  182.217758]  pci_device_remove+0x3e/0xc0
[  182.217761]  device_release_driver_internal+0xec/0x1b0
[  182.217762]  device_release_driver+0x12/0x20
[  182.217764]  pci_stop_bus_device+0x68/0x90
[  182.217766]  pci_stop_and_remove_bus_device_locked+0x1a/0x30
[  182.217767]  remove_store+0x7c/0x90
[  182.217770]  dev_attr_store+0x17/0x30
[  182.217772]  sysfs_kf_write+0x3c/0x50
[  182.217773]  kernfs_fop_write+0x125/0x1a0
[  182.217776]  __vfs_write+0x1b/0x40
[  182.217778]  vfs_write+0xb1/0x1a0
[  182.217779]  ksys_write+0xa7/0xe0
[  182.217780]  __x64_sys_write+0x1a/0x20
[  182.217783]  do_syscall_64+0x57/0x1c0
[  182.217785]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  182.217787] RIP: 0033:0x7f804b08f024
[  182.217788] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 
80 00 00 00 00 48 8d 05 b9 d3 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 
05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 49 89 d4 55 48 89 f5 53
[  182.217789] RSP: 002b:00007ffdbe4bc0b8 EFLAGS: 00000246 ORIG_RAX: 
0000000000000001
[  182.217790] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 
00007f804b08f024
[  182.217791] RDX: 0000000000000002 RSI: 000055bf20640470 RDI: 
0000000000000001
[  182.217792] RBP: 000055bf20640470 R08: 000000000000000a R09: 
0000000000008000
[  182.217792] R10: 000000000000000a R11: 0000000000000246 R12: 
00007f804b167760
[  182.217793] R13: 0000000000000002 R14: 00007f804b168560 R15: 
00007f804b167960
[  182.217795] ---[ end trace 292e6caf66ddf0df ]---
[  182.217797] [leaked fb] framebuffer[118]:
[  182.217798] [leaked fb] 	allocated by = gnome-shell
[  182.217799] [leaked fb] 	refcount=1
[  182.217801] [leaked fb] 	format=XR24 little-endian (0x34325258)
[  182.217802] [leaked fb] 	modifier=0x100000000000001
[  182.217803] [leaked fb] 	size=3200x1800
[  182.217803] [leaked fb] 	layers:
[  182.217805] [leaked fb] 		size[0]=3200x1800
[  182.217805] [leaked fb] 		pitch[0]=12800
[  182.217806] [leaked fb] 		offset[0]=0
[  182.217807] [leaked fb] 		obj[0]:
[  182.217808] [leaked fb] 			name=0
[  182.217809] [leaked fb] 			refcount=3
[  182.217810] [leaked fb] 			start=00000000
[  182.217810] [leaked fb] 			size=25165824
[  182.217811] [leaked fb] 			imported=no
[  182.241857] pci 0000:00:02.0: Removing from iommu group 1
[  182.241858] DMAR: DRHD: handling fault status reg 2
[  182.241864] DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff 
fault addr 0 [fault reason 02] Present bit in context entry is clear
[  189.181789] general protection fault: 0000 [#1] SMP PTI
[  189.181795] CPU: 0 PID: 836 Comm: gdbus Tainted: G        W 
5.4.0-rc2+ #2704
[  189.181797] Hardware name: Intel Corporation Skylake Client 
platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B105.B00.1512051901 
12/05/2015
[  189.181804] RIP: 0010:drm_mode_object_unregister+0xe/0x70
[  189.181806] Code: 54 00 4c 89 e7 e8 d2 d8 56 00 5b 41 5c 41 5d 5d c3 
90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 
53 <48> 8b 47 20 48 89 fb 49 89 f5 48 83 38 00 74 3a 4c 8d a3 d8 01 00
[  189.181809] RSP: 0018:ffffa1c481e73b60 EFLAGS: 00010246
[  189.181811] RAX: ffffffff9e502a90 RBX: ffff95c7da326e28 RCX: 
0000000000000001
[  189.181813] RDX: 0000000000000000 RSI: ffff95c7da326e18 RDI: 
f1ca50a8ff50515a
[  189.181815] RBP: ffffa1c481e73b78 R08: 0000000000000001 R09: 
0000000000000000
[  189.181817] R10: 0000000000000008 R11: ffff95c7dcf53770 R12: 
ffff95c7da326e00
[  189.181818] R13: ffffa1c481e73bf0 R14: ffff95c7e3cb7ac8 R15: 
ffff95c7e6cb23c0
[  189.181821] FS:  00007f688ccf1700(0000) GS:ffff95c7e7a00000(0000) 
knlGS:0000000000000000
[  189.181823] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  189.181825] CR2: 000056427674ff10 CR3: 000000015e376004 CR4: 
00000000003606f0
[  189.181826] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[  189.181828] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400
[  189.181829] Call Trace:
[  189.181834]  drm_framebuffer_free+0x21/0x40
[  189.181837]  drm_mode_object_put.part.2+0x3c/0x40
[  189.181839]  drm_mode_object_put+0x15/0x20
[  189.181841]  drm_fb_release+0xbc/0x130
[  189.181845]  drm_file_free.part.5+0x2ac/0x2e0
[  189.181847]  drm_close_helper.isra.6+0x60/0x70
[  189.181850]  drm_release+0x50/0x80
[  189.181853]  __fput+0xc6/0x260
[  189.181856]  ____fput+0xe/0x10
[  189.181859]  task_work_run+0x9d/0xc0
[  189.181862]  do_exit+0x2ed/0xbb0
[  189.181866]  ? poll_select_finish+0x210/0x210
[  189.181869]  do_group_exit+0x43/0xa0
[  189.181872]  get_signal+0x144/0x840
[  189.181876]  ? eventfd_read+0xe9/0x260
[  189.181879]  do_signal+0x34/0x6d0
[  189.181884]  exit_to_usermode_loop+0x8e/0x100
[  189.181887]  do_syscall_64+0x186/0x1c0
[  189.181890]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  189.181895] RIP: 0033:0x7f6895119729
[  189.181899] Code: Bad RIP value.
[  189.181901] RSP: 002b:00007f688ccf08a0 EFLAGS: 00000293 ORIG_RAX: 
0000000000000007
[  189.181903] RAX: fffffffffffffdfc RBX: 00007f687c023170 RCX: 
00007f6895119729
[  189.181905] RDX: 00000000ffffffff RSI: 0000000000000005 RDI: 
00007f687c023170
[  189.181906] RBP: 0000000000000005 R08: 0000000000000000 R09: 
0000000000000001
[  189.181908] R10: 000055cc6ed5dd80 R11: 0000000000000293 R12: 
00000000ffffffff
[  189.181909] R13: 00007f6895d8b4c0 R14: 00000000ffffffff R15: 
0000000000000005
[  189.181911] Modules linked in: nls_iso8859_1 snd_soc_skl 
snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core 
snd_soc_acpi_intel_match snd_soc_acpi snd_soc_core intel_rapl_msr 
snd_hda_codec_hdmi snd_hda_codec_realtek snd_compress 
snd_hda_codec_generic ledtrig_audio ac97_bus snd_pcm_dmaengine 
snd_hda_intel snd_intel_nhlt snd_hda_codec snd_hda_core snd_hwdep 
snd_pcm intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp 
kvm_intel kvm snd_seq_midi irqbypass snd_seq_midi_event snd_rawmidi 
crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iwlmvm snd_seq 
mac80211 libarc4 aesni_intel snd_seq_device snd_timer crypto_simd 
ipu3_cio2 cryptd glue_helper iwlwifi v4l2_fwnode intel_cstate 
videobuf2_dma_sg videobuf2_memops intel_rapl_perf asix videobuf2_v4l2 
videobuf2_common usbnet mii cfg80211 input_leds serio_raw 
intel_wmi_thunderbolt snd mei_me videodev soundcore 
intel_xhci_usb_role_switch mei 8250_dw mc roles intel_pch_thermal 
hid_sensor_magn_3d hid_sensor_accel_3d hid_sensor_press
[  189.181950]  hid_sensor_incl_3d hid_sensor_als hid_sensor_rotation 
hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer 
kfifo_buf hid_sensor_iio_common industrialio intel_vbtn mac_hid 
intel_hid acpi_pad sparse_keymap sch_fq_codel parport_pc ppdev lp 
parport ip_tables x_tables hid_sensor_custom hid_sensor_hub 
intel_ishtp_hid hid_generic dwc3 ulpi udc_core i2c_designware_platform 
i2c_designware_core e1000e psmouse i2c_i801 tg3 usbhid dwc3_pci hid 
intel_ish_ipc intel_lpss_pci intel_ishtp intel_lpss wmi 
pinctrl_sunrisepoint pinctrl_intel
[  189.181981] ---[ end trace 292e6caf66ddf0e0 ]---
[  189.201970] RIP: 0010:drm_mode_object_unregister+0xe/0x70
[  189.201975] Code: 54 00 4c 89 e7 e8 d2 d8 56 00 5b 41 5c 41 5d 5d c3 
90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 
53 <48> 8b 47 20 48 89 fb 49 89 f5 48 83 38 00 74 3a 4c 8d a3 d8 01 00
[  189.201978] RSP: 0018:ffffa1c481e73b60 EFLAGS: 00010246
[  189.201981] RAX: ffffffff9e502a90 RBX: ffff95c7da326e28 RCX: 
0000000000000001
[  189.201982] RDX: 0000000000000000 RSI: ffff95c7da326e18 RDI: 
f1ca50a8ff50515a
[  189.201984] RBP: ffffa1c481e73b78 R08: 0000000000000001 R09: 
0000000000000000
[  189.201986] R10: 0000000000000008 R11: ffff95c7dcf53770 R12: 
ffff95c7da326e00
[  189.201987] R13: ffffa1c481e73bf0 R14: ffff95c7e3cb7ac8 R15: 
ffff95c7e6cb23c0
[  189.201990] FS:  00007f688ccf1700(0000) GS:ffff95c7e7a00000(0000) 
knlGS:0000000000000000
[  189.201991] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  189.201993] CR2: 00007f68951196ff CR3: 000000015e376004 CR4: 
00000000003606f0
[  189.201995] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[  189.201997] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400

Best regards,
Baolu
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

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

[Janusz Krzysztofik]

Hi Baolu,

On Friday, October 11, 2019 8:54:09 AM CEST Lu Baolu wrote:
> Hi Janusz,
> 
> On 9/3/19 3:41 PM, 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. 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 $!
> > 
> 
> I tried to reproduce the issue with above instructions. I got below
> kernel messages after above operation. Is it the same as what you've
> seen? I can't find anything explicitly related to iommu except an IOMMU
> fault generated after device got removed and the DMA translation
> structures got torn down. Can you please help me to understand how IOMMU
> driver triggers the issue?
> 
> 
> [  182.217672] ------------[ cut here ]------------
> [  182.217679] WARNING: CPU: 1 PID: 1285 at 
> drivers/gpu/drm/drm_mode_config.c:495 drm_mode_config_cleanup+0x2cb/0x2e0
> [  182.217680] Modules linked in: nls_iso8859_1 snd_soc_skl 
> snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core 
> snd_soc_acpi_intel_match snd_soc_acpi snd_soc_core intel_rapl_msr 
> snd_hda_codec_hdmi snd_hda_codec_realtek snd_compress 
> snd_hda_codec_generic ledtrig_audio ac97_bus snd_pcm_dmaengine 
> snd_hda_intel snd_intel_nhlt snd_hda_codec snd_hda_core snd_hwdep 
> snd_pcm intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp 
> kvm_intel kvm snd_seq_midi irqbypass snd_seq_midi_event snd_rawmidi 
> crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iwlmvm snd_seq 
> mac80211 libarc4 aesni_intel snd_seq_device snd_timer crypto_simd 
> ipu3_cio2 cryptd glue_helper iwlwifi v4l2_fwnode intel_cstate 
> videobuf2_dma_sg videobuf2_memops intel_rapl_perf asix videobuf2_v4l2 
> videobuf2_common usbnet mii cfg80211 input_leds serio_raw 
> intel_wmi_thunderbolt snd mei_me videodev soundcore 
> intel_xhci_usb_role_switch mei 8250_dw mc roles intel_pch_thermal 
> hid_sensor_magn_3d hid_sensor_accel_3d hid_sensor_press
> [  182.217709]  hid_sensor_incl_3d hid_sensor_als hid_sensor_rotation 
> hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer 
> kfifo_buf hid_sensor_iio_common industrialio intel_vbtn mac_hid 
> intel_hid acpi_pad sparse_keymap sch_fq_codel parport_pc ppdev lp 
> parport ip_tables x_tables hid_sensor_custom hid_sensor_hub 
> intel_ishtp_hid hid_generic dwc3 ulpi udc_core i2c_designware_platform 
> i2c_designware_core e1000e psmouse i2c_i801 tg3 usbhid dwc3_pci hid 
> intel_ish_ipc intel_lpss_pci intel_ishtp intel_lpss wmi 
> pinctrl_sunrisepoint pinctrl_intel
> [  182.217727] CPU: 1 PID: 1285 Comm: bash Not tainted 5.4.0-rc2+ #2704
> [  182.217728] Hardware name: Intel Corporation Skylake Client 
> platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B105.B00.1512051901 
> 12/05/2015
> [  182.217731] RIP: 0010:drm_mode_config_cleanup+0x2cb/0x2e0
> [  182.217732] Code: eb 0c 48 8b 70 48 4c 89 e7 e8 31 f4 ff ff 48 8d 7d 
> a0 e8 d8 95 ff ff 48 85 c0 75 e6 48 8d 7d a0 e8 1a 87 ff ff e9 ef fd ff 
> ff <0f> 0b e9 ed fe ff ff 0f 0b eb 98 e8 05 ec 98 ff 0f 1f 44 00 00 0f
> [  182.217733] RSP: 0018:ffffa1c481d37c78 EFLAGS: 00010216
> [  182.217735] RAX: ffff95c7da326e08 RBX: ffff95c7dcf60000 RCX: 
> 000000008010000e
> [  182.217735] RDX: ffff95c7dcf603b8 RSI: 000000008010000e RDI: 
> ffff95c7dcf60390
> [  182.217736] RBP: ffffa1c481d37cd8 R08: 0000000000000000 R09: 
> ffffffff9e035e00
> [  182.217737] R10: ffffa1c481d37be0 R11: 0000000000000001 R12: 
> ffff95c7dcf60250
> [  182.217737] R13: ffff95c7dcf603b8 R14: ffffa1c481d37ee8 R15: 
> fffffffffffffff2
> [  182.217739] FS:  00007f804af7f740(0000) GS:ffff95c7e7a80000(0000) 
> knlGS:0000000000000000
> [  182.217739] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  182.217740] CR2: 00007ffebc530cec CR3: 0000000137e0e003 CR4: 
> 00000000003606e0
> [  182.217741] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [  182.217742] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
> 0000000000000400
> [  182.217742] Call Trace:
> [  182.217748]  ? _cond_resched+0x19/0x40
> [  182.217752]  intel_modeset_driver_remove+0xd1/0x150
> [  182.217754]  i915_driver_remove+0xb8/0x120
> [  182.217756]  i915_pci_remove+0x23/0x40
> [  182.217758]  pci_device_remove+0x3e/0xc0
> [  182.217761]  device_release_driver_internal+0xec/0x1b0
> [  182.217762]  device_release_driver+0x12/0x20
> [  182.217764]  pci_stop_bus_device+0x68/0x90
> [  182.217766]  pci_stop_and_remove_bus_device_locked+0x1a/0x30
> [  182.217767]  remove_store+0x7c/0x90
> [  182.217770]  dev_attr_store+0x17/0x30
> [  182.217772]  sysfs_kf_write+0x3c/0x50
> [  182.217773]  kernfs_fop_write+0x125/0x1a0
> [  182.217776]  __vfs_write+0x1b/0x40
> [  182.217778]  vfs_write+0xb1/0x1a0
> [  182.217779]  ksys_write+0xa7/0xe0
> [  182.217780]  __x64_sys_write+0x1a/0x20
> [  182.217783]  do_syscall_64+0x57/0x1c0
> [  182.217785]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  182.217787] RIP: 0033:0x7f804b08f024
> [  182.217788] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 
> 80 00 00 00 00 48 8d 05 b9 d3 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 
> 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 49 89 d4 55 48 89 f5 53
> [  182.217789] RSP: 002b:00007ffdbe4bc0b8 EFLAGS: 00000246 ORIG_RAX: 
> 0000000000000001
> [  182.217790] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 
> 00007f804b08f024
> [  182.217791] RDX: 0000000000000002 RSI: 000055bf20640470 RDI: 
> 0000000000000001
> [  182.217792] RBP: 000055bf20640470 R08: 000000000000000a R09: 
> 0000000000008000
> [  182.217792] R10: 000000000000000a R11: 0000000000000246 R12: 
> 00007f804b167760
> [  182.217793] R13: 0000000000000002 R14: 00007f804b168560 R15: 
> 00007f804b167960
> [  182.217795] ---[ end trace 292e6caf66ddf0df ]---
> [  182.217797] [leaked fb] framebuffer[118]:
> [  182.217798] [leaked fb] 	allocated by = gnome-shell

It looks like you may be trying to reproduce the issue with a graphics adapter 
which is occupied by a graphical environment.  While maybe this should be 
possible, other issues seem to interfere, making the picture less clear.  
Would you be able to try on an otherwise unused device?

Thanks,
Janusz

> [  182.217799] [leaked fb] 	refcount=1
> [  182.217801] [leaked fb] 	format=XR24 little-endian (0x34325258)
> [  182.217802] [leaked fb] 	modifier=0x100000000000001
> [  182.217803] [leaked fb] 	size=3200x1800
> [  182.217803] [leaked fb] 	layers:
> [  182.217805] [leaked fb] 		size[0]=3200x1800
> [  182.217805] [leaked fb] 		pitch[0]=12800
> [  182.217806] [leaked fb] 		offset[0]=0
> [  182.217807] [leaked fb] 		obj[0]:
> [  182.217808] [leaked fb] 			name=0
> [  182.217809] [leaked fb] 			refcount=3
> [  182.217810] [leaked fb] 			start=00000000
> [  182.217810] [leaked fb] 			size=25165824
> [  182.217811] [leaked fb] 			imported=no
> [  182.241857] pci 0000:00:02.0: Removing from iommu group 1
> [  182.241858] DMAR: DRHD: handling fault status reg 2
> [  182.241864] DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff 
> fault addr 0 [fault reason 02] Present bit in context entry is clear
> [  189.181789] general protection fault: 0000 [#1] SMP PTI
> [  189.181795] CPU: 0 PID: 836 Comm: gdbus Tainted: G        W 
> 5.4.0-rc2+ #2704
> [  189.181797] Hardware name: Intel Corporation Skylake Client 
> platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B105.B00.1512051901 
> 12/05/2015
> [  189.181804] RIP: 0010:drm_mode_object_unregister+0xe/0x70
> [  189.181806] Code: 54 00 4c 89 e7 e8 d2 d8 56 00 5b 41 5c 41 5d 5d c3 
> 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 
> 53 <48> 8b 47 20 48 89 fb 49 89 f5 48 83 38 00 74 3a 4c 8d a3 d8 01 00
> [  189.181809] RSP: 0018:ffffa1c481e73b60 EFLAGS: 00010246
> [  189.181811] RAX: ffffffff9e502a90 RBX: ffff95c7da326e28 RCX: 
> 0000000000000001
> [  189.181813] RDX: 0000000000000000 RSI: ffff95c7da326e18 RDI: 
> f1ca50a8ff50515a
> [  189.181815] RBP: ffffa1c481e73b78 R08: 0000000000000001 R09: 
> 0000000000000000
> [  189.181817] R10: 0000000000000008 R11: ffff95c7dcf53770 R12: 
> ffff95c7da326e00
> [  189.181818] R13: ffffa1c481e73bf0 R14: ffff95c7e3cb7ac8 R15: 
> ffff95c7e6cb23c0
> [  189.181821] FS:  00007f688ccf1700(0000) GS:ffff95c7e7a00000(0000) 
> knlGS:0000000000000000
> [  189.181823] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  189.181825] CR2: 000056427674ff10 CR3: 000000015e376004 CR4: 
> 00000000003606f0
> [  189.181826] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [  189.181828] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
> 0000000000000400
> [  189.181829] Call Trace:
> [  189.181834]  drm_framebuffer_free+0x21/0x40
> [  189.181837]  drm_mode_object_put.part.2+0x3c/0x40
> [  189.181839]  drm_mode_object_put+0x15/0x20
> [  189.181841]  drm_fb_release+0xbc/0x130
> [  189.181845]  drm_file_free.part.5+0x2ac/0x2e0
> [  189.181847]  drm_close_helper.isra.6+0x60/0x70
> [  189.181850]  drm_release+0x50/0x80
> [  189.181853]  __fput+0xc6/0x260
> [  189.181856]  ____fput+0xe/0x10
> [  189.181859]  task_work_run+0x9d/0xc0
> [  189.181862]  do_exit+0x2ed/0xbb0
> [  189.181866]  ? poll_select_finish+0x210/0x210
> [  189.181869]  do_group_exit+0x43/0xa0
> [  189.181872]  get_signal+0x144/0x840
> [  189.181876]  ? eventfd_read+0xe9/0x260
> [  189.181879]  do_signal+0x34/0x6d0
> [  189.181884]  exit_to_usermode_loop+0x8e/0x100
> [  189.181887]  do_syscall_64+0x186/0x1c0
> [  189.181890]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  189.181895] RIP: 0033:0x7f6895119729
> [  189.181899] Code: Bad RIP value.
> [  189.181901] RSP: 002b:00007f688ccf08a0 EFLAGS: 00000293 ORIG_RAX: 
> 0000000000000007
> [  189.181903] RAX: fffffffffffffdfc RBX: 00007f687c023170 RCX: 
> 00007f6895119729
> [  189.181905] RDX: 00000000ffffffff RSI: 0000000000000005 RDI: 
> 00007f687c023170
> [  189.181906] RBP: 0000000000000005 R08: 0000000000000000 R09: 
> 0000000000000001
> [  189.181908] R10: 000055cc6ed5dd80 R11: 0000000000000293 R12: 
> 00000000ffffffff
> [  189.181909] R13: 00007f6895d8b4c0 R14: 00000000ffffffff R15: 
> 0000000000000005
> [  189.181911] Modules linked in: nls_iso8859_1 snd_soc_skl 
> snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core 
> snd_soc_acpi_intel_match snd_soc_acpi snd_soc_core intel_rapl_msr 
> snd_hda_codec_hdmi snd_hda_codec_realtek snd_compress 
> snd_hda_codec_generic ledtrig_audio ac97_bus snd_pcm_dmaengine 
> snd_hda_intel snd_intel_nhlt snd_hda_codec snd_hda_core snd_hwdep 
> snd_pcm intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp 
> kvm_intel kvm snd_seq_midi irqbypass snd_seq_midi_event snd_rawmidi 
> crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iwlmvm snd_seq 
> mac80211 libarc4 aesni_intel snd_seq_device snd_timer crypto_simd 
> ipu3_cio2 cryptd glue_helper iwlwifi v4l2_fwnode intel_cstate 
> videobuf2_dma_sg videobuf2_memops intel_rapl_perf asix videobuf2_v4l2 
> videobuf2_common usbnet mii cfg80211 input_leds serio_raw 
> intel_wmi_thunderbolt snd mei_me videodev soundcore 
> intel_xhci_usb_role_switch mei 8250_dw mc roles intel_pch_thermal 
> hid_sensor_magn_3d hid_sensor_accel_3d hid_sensor_press
> [  189.181950]  hid_sensor_incl_3d hid_sensor_als hid_sensor_rotation 
> hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer 
> kfifo_buf hid_sensor_iio_common industrialio intel_vbtn mac_hid 
> intel_hid acpi_pad sparse_keymap sch_fq_codel parport_pc ppdev lp 
> parport ip_tables x_tables hid_sensor_custom hid_sensor_hub 
> intel_ishtp_hid hid_generic dwc3 ulpi udc_core i2c_designware_platform 
> i2c_designware_core e1000e psmouse i2c_i801 tg3 usbhid dwc3_pci hid 
> intel_ish_ipc intel_lpss_pci intel_ishtp intel_lpss wmi 
> pinctrl_sunrisepoint pinctrl_intel
> [  189.181981] ---[ end trace 292e6caf66ddf0e0 ]---
> [  189.201970] RIP: 0010:drm_mode_object_unregister+0xe/0x70
> [  189.201975] Code: 54 00 4c 89 e7 e8 d2 d8 56 00 5b 41 5c 41 5d 5d c3 
> 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 
> 53 <48> 8b 47 20 48 89 fb 49 89 f5 48 83 38 00 74 3a 4c 8d a3 d8 01 00
> [  189.201978] RSP: 0018:ffffa1c481e73b60 EFLAGS: 00010246
> [  189.201981] RAX: ffffffff9e502a90 RBX: ffff95c7da326e28 RCX: 
> 0000000000000001
> [  189.201982] RDX: 0000000000000000 RSI: ffff95c7da326e18 RDI: 
> f1ca50a8ff50515a
> [  189.201984] RBP: ffffa1c481e73b78 R08: 0000000000000001 R09: 
> 0000000000000000
> [  189.201986] R10: 0000000000000008 R11: ffff95c7dcf53770 R12: 
> ffff95c7da326e00
> [  189.201987] R13: ffffa1c481e73bf0 R14: ffff95c7e3cb7ac8 R15: 
> ffff95c7e6cb23c0
> [  189.201990] FS:  00007f688ccf1700(0000) GS:ffff95c7e7a00000(0000) 
> knlGS:0000000000000000
> [  189.201991] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  189.201993] CR2: 00007f68951196ff CR3: 000000015e376004 CR4: 
> 00000000003606f0
> [  189.201995] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [  189.201997] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
> 0000000000000400
> 
> Best regards,
> Baolu
> 




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