Re: [PATCH v3 5/8] iommufd: Associate fault object with iommufd_hw_pgtable

[Baolu Lu]

On 3/9/24 3:05 AM, Jason Gunthorpe wrote:
> On Mon, Jan 22, 2024 at 03:39:00PM +0800, Lu Baolu wrote:
>
> > @@ -411,6 +414,8 @@ enum iommu_hwpt_data_type {
> >    * @__reserved: Must be 0
> >    * @data_type: One of enum iommu_hwpt_data_type
> >    * @data_len: Length of the type specific data
> > + * @fault_id: The ID of IOMMUFD_FAULT object. Valid only if flags field of
> > + *            IOMMU_HWPT_FAULT_ID_VALID is set.
> >    * @data_uptr: User pointer to the type specific data
> >    *
> >    * Explicitly allocate a hardware page table object. This is the same object
> > @@ -441,6 +446,7 @@ struct iommu_hwpt_alloc {
> >   	__u32 __reserved;
> >   	__u32 data_type;
> >   	__u32 data_len;
> > +	__u32 fault_id;
> >   	__aligned_u64 data_uptr;
> >   };
>
> ?? We can't add fault_id in the middle of the struct??

Yes. I should add the new field at the end.

By the way, with a __u32 added, this data structure is not 64-byte-
aligned anymore. Do we need to add another unused u32 entry, or just let
the compiler handle it?

> > +	if (cmd->flags & IOMMU_HWPT_FAULT_ID_VALID) {
> > +		struct iommufd_fault *fault;
> > +
> > +		fault = iommufd_get_fault(ucmd, cmd->fault_id);
> > +		if (IS_ERR(fault)) {
> > +			rc = PTR_ERR(fault);
> > +			goto out_hwpt;
> > +		}
> > +		hwpt->fault = fault;
> > +		hwpt->domain->iopf_handler = iommufd_fault_iopf_handler;
> > +		hwpt->domain->fault_data = hwpt;
> > +		hwpt->fault_capable = true;
>
> I wonder if there should be an iommu API to make a domain fault
> capable?

The iommu core identifies a fault-capable domain by checking its
domain->iopf_handler. Anyway, what's the difference between a fault or
non-fault capable domain from iommu core's point of view?

Best regards,
baolu