RE: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc_user op

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Tuesday, October 17, 2023 4:52 PM
> 
> On 2023/10/17 02:17, Nicolin Chen wrote:
> > On Mon, Oct 16, 2023 at 08:54:07AM -0300, Jason Gunthorpe wrote:
> >> 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?
> >
> > The invalidation data has hwpt_id so it's tied to a hwpt and its
> > hwpt->domain. Would it be reasonable to have a different type of
> > invalidation data for the same type of hwpt?
> 
> this seems like what Jason asks. A type of hwpt can have two kinds
> of invalidation data types. Is it really possible?
> 

e.g. vhost-iommu may want its own vendor-agnostic format from
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