Re: [PATCH v2 3/6] iommufd: Initializing and releasing IO page fault data

[Baolu Lu]

On 12/12/23 10:12 PM, Jason Gunthorpe wrote:
> On Tue, Dec 12, 2023 at 02:10:08PM +0100, Joel Granados wrote:
>
> > > diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> > > index 645ab5d290fe..0a8e03d5e7c5 100644
> > > --- a/drivers/iommu/iommufd/device.c
> > > +++ b/drivers/iommu/iommufd/device.c
> > > @@ -456,6 +456,16 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
> > >   	if (rc)
> > >   		goto err_unlock;
> > >   
> > > +	if (hwpt->fault) {
> > > +		void *curr;
> > > +
> > > +		curr = iopf_pasid_cookie_set(idev->dev, IOMMU_NO_PASID, idev);
> > I'm hitting an error here when I try to attach to a hwpt that I created
> > previously with the `IOMMU_HWPT_ALLOC_IOPF_CAPABLE` flag.
> >
> > I get an -ENODEV from iopf_pasid_cookie_set which is triggered by
> > dev->iommu->fault_param being 0x0.
> >
> > I looked around and I see that the fault param gets set in
> > iopf_queue_add_device which is called from iommu_dev_enable_feature
> > only. Furthermore iommu_dev_enable_feature is only called in idxd and
> > uacce drivers.
> >
> > Questions:
> > 1. Should iopf_queue_add_device get called from the
> >     IOMMU_HWPT_ALLOC_IOPF_CAPABLE ioctl call? This make sense to me as
> >     this is where the device and the IOPF are related from user space.
> It probably needs to call the set feature thing in the short term.
>
> In the medium term I would like the drivers to manage the iopf based
> on domain attachment not explicit feature asks

Yes, it's the same as my plan.

> > 2. This is not intended to work only with idxd and uacce. right?
> It should work everywhere, I suspect Intel Team didn't hit this
> because they are testing IDXD SIOV?

Yes.

> Can you guys also test it as a PF
> assignment?

For PF assignment, probably the driver (vfio-pci) needs to enable iopf.

Best regards,
baolu