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Date:   Tue, 24 Oct 2023 14:31:39 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Nicolin Chen <nicolinc@nvidia.com>
Cc:     Yi Liu <yi.l.liu@intel.com>, joro@8bytes.org,
        alex.williamson@redhat.com, kevin.tian@intel.com,
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        zhenzhong.duan@intel.com, joao.m.martins@oracle.com
Subject: Re: [PATCH v6 07/10] iommufd: Add a nested HW pagetable object
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On Tue, Oct 24, 2023 at 10:28:45AM -0700, Nicolin Chen wrote:
> On Tue, Oct 24, 2023 at 02:18:10PM -0300, Jason Gunthorpe wrote:
> > On Tue, Oct 24, 2023 at 08:06:06AM -0700, Yi Liu wrote:
> > > @@ -195,6 +279,10 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
> > >  	if (pt_obj->type == IOMMUFD_OBJ_IOAS) {
> > >  		struct iommufd_hwpt_paging *hwpt_paging;
> > >  
> > > +		if (cmd->data_type != IOMMU_HWPT_DATA_NONE) {
> > > +			rc = -EINVAL;
> > > +			goto out_put_pt;
> > > +		}
> > >  		ioas = container_of(pt_obj, struct iommufd_ioas, obj);
> > >  		mutex_lock(&ioas->mutex);
> > >  		hwpt_paging = iommufd_hwpt_paging_alloc(ucmd->ictx, ioas, idev,
> > 
> > ?? What is this?
> > 
> > Ah something went wrong earlier in "iommu: Pass in parent domain with
> > user_data to domain_alloc_user op"
> > 
> > Once we added the user_data we should flow it through to the op
> > always.
> 
> Hmm, iommufd_hwpt_paging_alloc doesn't take (or need) user_data,
> but we could pass in a dummy one if that looks better?

The point is for the user_data to always be available, the driver
needs to check it if it is passed.

This should all be plumbed to allow drivers to also customize their
paging domains too.

Jason