Re: [PATCH 3/9] iommu: Add common code to handle IO page faults

[Baolu Lu]

On 2023/7/12 4:50, Jacob Pan wrote:
> Hi Lu,
>
> On Tue, 11 Jul 2023 09:06:36 +0800, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> wrote:
>
> > The individual iommu drivers report iommu faults by calling
> > iommu_report_device_fault(), where a pre-registered device fault handler
> > is called to route the fault to another fault handler installed on the
> > corresponding iommu domain.
> >
> > The pre-registered device fault handler is static and won't be dynamic
> > as the fault handler is eventually per iommu domain. Replace the device
> > fault handler with a static common code to avoid unnecessary code.
> >
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/iommu.c | 24 +++++++++++++++++++++++-
> >   1 file changed, 23 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index da340f11c5f5..41328f03e8b4 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -1278,6 +1278,28 @@ int iommu_unregister_device_fault_handler(struct
> > device *dev) }
> >   EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> >   
> > +static int iommu_handle_io_pgfault(struct device *dev,
> > +				   struct iommu_fault *fault)
> > +{
> > +	struct iommu_domain *domain;
> > +
> > +	if (fault->type != IOMMU_FAULT_PAGE_REQ)
> > +		return -EINVAL;
> > +
> > +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
> > +		domain = iommu_get_domain_for_dev_pasid(dev,
> > fault->prm.pasid, 0);
> > +	else
> > +		domain = iommu_get_domain_for_dev(dev);
> we don't support IOPF w/o PASID yet, right?

It's the individual driver that decides whether iopf w/o pasid is
supported or not. The iommu core doesn't need to make such assumption.

> > +
> > +	if (!domain || !domain->iopf_handler)
> > +		return -ENODEV;
> > +
> > +	if (domain->iopf_handler == iommu_sva_handle_iopf)
> > +		return iommu_queue_iopf(fault, dev);
> Just wondering why have a special treatment for SVA domain. Can
> iommu_queue_iopf() be used as SVA domain->iopf_handler?

Yes. I will make this change according to Kevin's suggestion in this
thread.

> > +
> > +	return domain->iopf_handler(fault, dev, domain->fault_data);
> > +}
> > +
> >   /**
> >    * iommu_report_device_fault() - Report fault event to device driver
> >    * @dev: the device
> > @@ -1320,7 +1342,7 @@ int iommu_report_device_fault(struct device *dev,
> > struct iommu_fault_event *evt) mutex_unlock(&fparam->lock);
> >   	}
> >   
> > -	ret = fparam->handler(&evt->fault, fparam->data);
> > +	ret = iommu_handle_io_pgfault(dev, &evt->fault);
> >   	if (ret && evt_pending) {
> >   		mutex_lock(&fparam->lock);
> >   		list_del(&evt_pending->list);
>
>
> Thanks,
>
> Jacob

Best regards,
baolu