[PATCH 3/3] iommu: Allow drivers to say if they use report_iommu_fault()

[Jason Gunthorpe]

On Thu, Oct 23, 2025 at 11:54:34AM -0300, Jason Gunthorpe wrote:
> On Thu, Oct 23, 2025 at 12:24:01PM +0100, Robin Murphy wrote:
> > On 2025-10-22 6:12 pm, Jason Gunthorpe wrote:
> > > report_iommu_fault() is an older API that has been superseded by
> > > iommu_report_device_fault() which is capable to support PRI.
> > > 
> > > Only two external drivers consume this, drivers/remoteproc and
> > > drivers/gpu/drm/msm. Ideally they would move over to the new APIs, but for
> > > now protect against accidentally mix and matching the wrong components.
> > > 
> > > The iommu drivers support either the old iommu_set_fault_handler() via the
> > > driver calling report_iommu_fault(), or they are newer server focused
> > > drivers that call iommu_report_device_fault().
> > > 
> > > Include a flag in the domain_ops if it calls report_iommu_fault() and
> > > block iommu_set_fault_handler() on iommu's that can't support it.
> > 
> > This isn't a domain operation though; depending on how you look at it,
> > supporting a legacy fault_handler is either a capability of the IOMMU driver
> > (that would be reachable via domain->owner->capable) or a property of the
> > iommu_domain itself that the drivers can set at allocation time (basically
> > this same patch just with the lines in slightly different places).
> 
> That's right, the issue is:
> 
> void iommu_set_fault_handler(struct iommu_domain *domain,
> 					iommu_fault_handler_t handler,
> 					void *token)
> 
> We can't get to the iommu instance starting from a domain pointer
> 
> Do you think we should change the above signature to include a
> struct device *?

Reading this again, it is easy to move it to the domain->owner, which
is an *ops* pointer. It would still be driver global and not
per-instance. Lets try that then

I like adding a iommu_paging_domain_alloc_flags() option too..

Jason