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

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Sep 26, 2023 at 06:37:55AM +0000, Tian, Kevin wrote:
> > From: Robin Murphy <robin.murphy@arm.com>
> > Sent: Friday, September 22, 2023 5:48 PM
> > 
> > I could go on enjoying myself, but basically yeah, "default" can't be a
> > type in itself (at best it would be a meta-type which could be
> > requested, such that it resolves to some real type to actually
> > allocate), so a good name should reflect what the type functionally
> > *means* to the user. IIUC the important distinction is that it's an
> > abstract kernel-owned pagetable for the user to indirectly control via
> > the API, rather than one it owns and writes directly (and thus has to be
> > in a specific agreed format).
> > 
> 
> IOMMU_HWPT_TYPE_KERNEL then?
> 
> IOMMU_HWPT_TYPE_GENERIC also doesn't sound a straight word.

At the end of the day this enum is the type tag for:

 struct iommu_hwpt_alloc {
 	__u32 size;
 	__u32 pt_id;
 	__u32 out_hwpt_id;
 	__u32 __reserved;
+	__u32 hwpt_type;
+	__u32 data_len;
+	__aligned_u64 data_uptr;
 };

That pointer.

IOMMU_HWPT_ALLOC_DATA_NONE = 0
IOMMU_HWPT_ALLOC_DATA_INTEL_VTD
IOMMU_HWPT_ALLOC_DATA_ARM_SMMUV3

etc?

DATA_NONE requires data_len == 0

Jason