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Date:   Tue, 12 Dec 2023 10:12:08 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Joel Granados <j.granados@samsung.com>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Nicolin Chen <nicolinc@nvidia.com>,
        Yi Liu <yi.l.liu@intel.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        iommu@lists.linux.dev, linux-kselftest@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/6] iommufd: Initializing and releasing IO page fault
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Message-ID: <20231212141208.GA3013885@ziepe.ca>
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On Tue, Dec 12, 2023 at 02:10:08PM +0100, Joel Granados wrote:

> > diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> > index 645ab5d290fe..0a8e03d5e7c5 100644
> > --- a/drivers/iommu/iommufd/device.c
> > +++ b/drivers/iommu/iommufd/device.c
> > @@ -456,6 +456,16 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
> >  	if (rc)
> >  		goto err_unlock;
> >  
> > +	if (hwpt->fault) {
> > +		void *curr;
> > +
> > +		curr = iopf_pasid_cookie_set(idev->dev, IOMMU_NO_PASID, idev);
> I'm hitting an error here when I try to attach to a hwpt that I created
> previously with the `IOMMU_HWPT_ALLOC_IOPF_CAPABLE` flag.
> 
> I get an -ENODEV from iopf_pasid_cookie_set which is triggered by
> dev->iommu->fault_param being 0x0.
> 
> I looked around and I see that the fault param gets set in
> iopf_queue_add_device which is called from iommu_dev_enable_feature
> only. Furthermore iommu_dev_enable_feature is only called in idxd and
> uacce drivers.
> 
> Questions:
> 1. Should iopf_queue_add_device get called from the
>    IOMMU_HWPT_ALLOC_IOPF_CAPABLE ioctl call? This make sense to me as
>    this is where the device and the IOPF are related from user space.

It probably needs to call the set feature thing in the short term.

In the medium term I would like the drivers to manage the iopf based
on domain attachment not explicit feature asks

> 2. This is not intended to work only with idxd and uacce. right?

It should work everywhere, I suspect Intel Team didn't hit this
because they are testing IDXD SIOV? Can you guys also test it as a PF
assignment?

Jason