Re: [PATCH v5 14/23] iommu: introduce page response function

Jacob Pan
2018-05-29T16:10:29Z

On Mon, 14 May 2018 14:39:51 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Hi,
>
> On 05/12/2018 04:54 AM, Jacob Pan wrote:
> > IO page faults can be handled outside IOMMU subsystem. For an
> > example, when nested translation is turned on and guest owns the
> > first level page tables, device page request can be forwared
> > to the guest for handling faults. As the page response returns
> > by the guest, IOMMU driver on the host need to process the
> > response which informs the device and completes the page request
> > transaction.
> >
> > This patch introduces generic API function for page response
> > passing from the guest or other in-kernel users. The definitions of
> > the generic data is based on PCI ATS specification not limited to
> > any vendor.
> >
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Link: https://lkml.org/lkml/2017/12/7/1725
> > ---
> > drivers/iommu/iommu.c | 45
> > +++++++++++++++++++++++++++++++++++++++++++++ include/linux/iommu.h
> > | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed,
> > 88 insertions(+)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index b3f9daf..02fed3e 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -1533,6 +1533,51 @@ int iommu_sva_invalidate(struct iommu_domain
> > *domain, }
> > EXPORT_SYMBOL_GPL(iommu_sva_invalidate);
> >
> > +int iommu_page_response(struct device *dev,
> > + struct page_response_msg *msg)
> > +{
> > + struct iommu_param *param = dev->iommu_param;
> > + int ret = -EINVAL;
> > + struct iommu_fault_event *evt;
> > + struct iommu_domain *domain =
> > iommu_get_domain_for_dev(dev); +
> > + if (!domain || !domain->ops->page_response)
> > + return -ENODEV;
> > +
> > + /*
> > + * Device iommu_param should have been allocated when
> > device is
> > + * added to its iommu_group.
> > + */
> > + if (!param || !param->fault_param)
> > + return -EINVAL;
> > +
> > + /* Only send response if there is a fault report pending */
> > + mutex_lock(&param->fault_param->lock);
> > + if (list_empty(&param->fault_param->faults)) {
> > + pr_warn("no pending PRQ, drop response\n");
> > + goto done_unlock;
> > + }
> > + /*
> > + * Check if we have a matching page request pending to
> > respond,
> > + * otherwise return -EINVAL
> > + */
> > + list_for_each_entry(evt, &param->fault_param->faults,
> > list) {
> > + if (evt->pasid == msg->pasid &&
> > + msg->page_req_group_id ==
> > evt->page_req_group_id) {
> > + msg->private_data = evt->iommu_private;
> > + ret = domain->ops->page_response(dev, msg);
> > + list_del(&evt->list);
> > + kfree(evt);
> > + break;
> > + }
> > + }
>
> Are above two checks duplicated? We won't find a matching
> request if the list is empty. And we need to printk a message
> if we can't find the matching request.
>
sorry about the delay. I am not sure which two checks, we only search
for pending page request if the list is not empty.
Yes, it is a good idea to print out warning if the page response has no
match request.
> Best regards,
> Lu Baolu
>
> [...]
>

[Jacob Pan]