iommupt/vtd: Support dirty tracking on PASID

[PATCH 0/3] iommupt/vtd: Support dirty tracking on PASID

Posted by Zhenzhong Duan 2 days, 12 hours ago

Hi,

When we add pasid support in QEMU for passthrough device, we found
PASID attachment to a nested parent domain with dirty tracking failed.

It's because PASID-level dirty tracking is not there yet, by adding it,
we can enable PASID attachment to such domain.

Thanks
Zhenzhong


Zhenzhong Duan (3):
  iommupt/vtd: Pass dmar_domain pointer to device_set_dirty_tracking()
  iommupt/vtd: Support dirty tracking on PASID
  iommufd/selftest: Test dirty tracking on PASID

 drivers/iommu/intel/iommu.c             | 33 ++++++++++++++-----------
 tools/testing/selftests/iommu/iommufd.c | 27 ++++++++++++++++++++
 2 files changed, 45 insertions(+), 15 deletions(-)

-- 
2.47.3

Re: [PATCH 0/3] iommupt/vtd: Support dirty tracking on PASID

Posted by Jason Gunthorpe 1 day, 14 hours ago

On Wed, Feb 04, 2026 at 09:34:01PM -0500, Zhenzhong Duan wrote:
> Hi,
> 
> When we add pasid support in QEMU for passthrough device, we found
> PASID attachment to a nested parent domain with dirty tracking failed.
> 
> It's because PASID-level dirty tracking is not there yet, by adding it,
> we can enable PASID attachment to such domain.
> 
> Thanks
> Zhenzhong
> 
> 
> Zhenzhong Duan (3):
>   iommupt/vtd: Pass dmar_domain pointer to device_set_dirty_tracking()
>   iommupt/vtd: Support dirty tracking on PASID
>   iommufd/selftest: Test dirty tracking on PASID

I'm not sure why you marked this s iommupt? It isn't right?

Also only the second stage table supports dirty tracking so I'm
confused what is the issue? Is it trying to say that if a second stage
is written to a pasid entry on a !=0 pasid path it doesn't work right?
But it does work on a 0 pasid?

Huh?

That sounds like a systemic problem, the two flows shouldn't actually
be any different.

Jason

RE: [PATCH 0/3] iommupt/vtd: Support dirty tracking on PASID

Posted by Duan, Zhenzhong 1 day, 11 hours ago


>-----Original Message-----
>From: Jason Gunthorpe <jgg@ziepe.ca>
>Subject: Re: [PATCH 0/3] iommupt/vtd: Support dirty tracking on PASID
>
>On Wed, Feb 04, 2026 at 09:34:01PM -0500, Zhenzhong Duan wrote:
>> Hi,
>>
>> When we add pasid support in QEMU for passthrough device, we found
>> PASID attachment to a nested parent domain with dirty tracking failed.
>>
>> It's because PASID-level dirty tracking is not there yet, by adding it,
>> we can enable PASID attachment to such domain.
>>
>> Thanks
>> Zhenzhong
>>
>>
>> Zhenzhong Duan (3):
>>   iommupt/vtd: Pass dmar_domain pointer to device_set_dirty_tracking()
>>   iommupt/vtd: Support dirty tracking on PASID
>>   iommufd/selftest: Test dirty tracking on PASID
>
>I'm not sure why you marked this s iommupt? It isn't right?

Oops, should be iommu/vtd.

>
>Also only the second stage table supports dirty tracking so I'm
>confused what is the issue? Is it trying to say that if a second stage
>is written to a pasid entry on a !=0 pasid path it doesn't work right?

Yes, more strictly, if a second stage domain flagged with
IOMMU_HWPT_ALLOC_DIRTY_TRACKING is written to a pasid entry
on a !=0 pasid, it's not allowed currently, by below check:

static int intel_iommu_set_dev_pasid()
{
...
        if (domain->dirty_ops)
                return -EINVAL;


>But it does work on a 0 pasid?

More strictly, it works on IOMMU_NO_PASID.
For IOMMU_NO_PASID, we trigger attach_dev(), for other pasids,
We trigger set_dev_pasid().

>
>Huh?
>
>That sounds like a systemic problem, the two flows shouldn't actually
>be any different.

Yes, just because we have code to setup dirty tracking on 0 pasid entry
but lack the same code for !=0 pasid entry in VTD.

0 pasid is special that it can also be IOMMU_NO_PASID if PASID isn't supported.

Thanks
Zhenzhong