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

[Yi Liu]

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?

> With this being asked, I added it for our next version. At this
> moment, it only does a sanity job:
>
> // API
> __iommu_copy_struct_from_user(void *dst_data,
> 			      const struct iommu_user_data *src_data,
> 			      unsigned int data_type, size_t data_len,
> 			      size_t min_len)
> {
> 	if (src_data->type != data_type)
> 		return -EINVAL;
>
> // Caller
> 	rc = iommu_copy_struct_from_user(&user_cfg, user_data,
> 					 IOMMU_HWPT_DATA_SELFTEST, iotlb);
> 	if (rc)
> 		return ERR_PTR(rc);
>
> Thanks
> Nic

--
Regards,
Yi Liu