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Date:   Mon, 16 Oct 2023 08:54:07 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Yi Liu <yi.l.liu@intel.com>
Cc:     Nicolin Chen <nicolinc@nvidia.com>, joro@8bytes.org,
        alex.williamson@redhat.com, kevin.tian@intel.com,
        robin.murphy@arm.com, baolu.lu@linux.intel.com, cohuck@redhat.com,
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        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        zhenzhong.duan@intel.com, joao.m.martins@oracle.com
Subject: Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for
 domain_alloc_user op
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On Mon, Oct 16, 2023 at 11:28:15AM +0800, Yi Liu wrote:
> On 2023/10/14 01:56, Nicolin Chen wrote:
> > On Fri, Oct 13, 2023 at 11:04:56AM -0300, Jason Gunthorpe wrote:
> > > On Fri, Oct 13, 2023 at 12:33:13PM +0800, Yi Liu wrote:
> > > 
> > > > not really. Below the users of the struct iommu_user_data in my current
> > > > iommufd_nesting branch. Only the domain_alloc_user op has type as there
> > > > can be multiple vendor specific alloc data types. Basically, I'm ok to
> > > > make the change you suggested, just not sure if it is good to add type
> > > > as it is only needed by one path.
> > > 
> > > I don't think we should ever have an opaque data blob without a type
> > > tag..
> > 
> > I can add those "missing" data types, and then a driver will be
> > responsible for sanitizing the type along with the data_len.
> > 
> > I notice that the enum iommu_hwpt_data_type in the posted patch
> > is confined to the alloc_user uAPI. Perhaps we should share it
> > with invalidate too:
> 
> invalidation path does not need a type field today as the data
> type is vendor specific, vendor driver should know the data type
> when calls in.

I'm not keen on that, what if a driver needs another type in the
future?  You'd want to make the invalidation data format part of the
domain allocation?

Jason