Re: [PATCH RFC v1 03/11] iommu/virtio: Handle incoming page faults

[Vivek Kumar Gautam]

Hi Jean,


On 10/11/21 2:46 PM, Jean-Philippe Brucker wrote:
> Hi Vivek,
>
> On Mon, Oct 11, 2021 at 01:41:15PM +0530, Vivek Gautam wrote:
> > > > +     list_for_each_entry(ep, &viommu->endpoints, list) {
> > > > +             if (ep->eid == endpoint) {
> > > > +                     vdev = ep->vdev;
> >
> > I have a question here though -
> > Is endpoint-ID unique across all the endpoints available per 'viommu_dev' or
> > per 'viommu_domain'?
> > If it is per 'viommu_domain' then the above list is also incorrect.
> > As you pointed to in the patch [1] -
> > [PATCH RFC v1 02/11] iommu/virtio: Maintain a list of endpoints served
> > by viommu_dev
> > I am planning to add endpoint ID into a static global xarray in
> > viommu_probe_device() as below:
> >
> >          vdev_for_each_id(i, eid, vdev) {
> >                  ret = xa_insert(&viommu_ep_ids, eid, vdev, GFP_KERNEL);
> >                  if (ret)
> >                          goto err_free_dev;
> >          }
> >
> > and replace the above list traversal as below:
> >
> >                  xa_lock_irqsave(&viommu_ep_ids, flags);
> >                  xa_for_each(&viommu_ep_ids, eid, vdev) {
> >                          if (eid == endpoint) {
> >                                  ret =
> > iommu_report_device_fault(vdev->dev, &fault_evt);
> >                                  if (ret)
> >                                          dev_err(vdev->dev, "Couldn't
> > handle page request\n");
> >                          }
> >                  }
> >                  xa_unlock_irqrestore(&viommu_ep_ids, flags);
> >
> > But using a global xarray would also be incorrect if the endpointsID are global
> > across 'viommu_domain'.
> >
> > I need to find the correct 'viommu_endpoint' to call iommu_report_device_fault()
> > with the correct device.
>
> The endpoint IDs are only unique across viommu_dev, so a global xarray
> wouldn't work but one in viommu_dev would. In vdomain it doesn't work
> either because we can't get to the domain from the fault handler without
> first finding the endpoint

Thanks. That's easy then. Will have a xarray in viommu_dev and iterate 
over it from the fault handler.

Best regards
Vivek