Re: [PATCH 2/5] iommu: Set PCI_BUS_FLAGS_MSI_REMAP if IOMMU have capability of IRQ remapping

[Yongji Xie]

On 2016/5/25 5:11, Bjorn Helgaas wrote:

> On Wed, Apr 27, 2016 at 08:43:27PM +0800, Yongji Xie wrote:
> > The capability of IRQ remapping is abstracted on IOMMU side on
> > some archs. There is a existing flag IOMMU_CAP_INTR_REMAP for this.
> >
> > To have a universal flag to test this capability for different
> > archs on PCI side, we set PCI_BUS_FLAGS_MSI_REMAP for PCI buses
> > when IOMMU_CAP_INTR_REMAP is set.
> >
> > Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/iommu.c |   15 +++++++++++++++
> >   1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 0e3b009..5d2b6f6 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -813,6 +813,16 @@ struct iommu_group *pci_device_group(struct device *dev)
> >   	return group;
> >   }
> >   
> > +static void pci_check_msi_remapping(struct pci_dev *pdev,
> > +					const struct iommu_ops *ops)
> > +{
> > +	struct pci_bus *bus = pdev->bus;
> > +
> > +	if (ops->capable(IOMMU_CAP_INTR_REMAP) &&
> > +		!(bus->bus_flags & PCI_BUS_FLAGS_MSI_REMAP))
> > +		bus->bus_flags |= PCI_BUS_FLAGS_MSI_REMAP;
> > +}
> This looks an awful lot like the pci_bus_check_msi_remapping() you add
> elsewhere.  Why do we need both?

I will modify this function as you suggested.  And we add this function
here because some iommu drivers would be initialed after PCI probing.

> >   /**
> >    * iommu_group_get_for_dev - Find or create the IOMMU group for a device
> >    * @dev: target device
> > @@ -871,6 +881,9 @@ static int add_iommu_group(struct device *dev, void *data)
> >   	const struct iommu_ops *ops = cb->ops;
> >   	int ret;
> >   
> > +	if (dev_is_pci(dev) && ops->capable)
> > +		pci_check_msi_remapping(to_pci_dev(dev), ops);
> > +
> >   	if (!ops->add_device)
> >   		return 0;
> >   
> > @@ -913,6 +926,8 @@ static int iommu_bus_notifier(struct notifier_block *nb,
> >   	 * result in ADD/DEL notifiers to group->notifier
> >   	 */
> >   	if (action == BUS_NOTIFY_ADD_DEVICE) {
> > +		if (dev_is_pci(dev) && ops->capable)
> > +			pci_check_msi_remapping(to_pci_dev(dev), ops);
> These calls don't smell right either.  Why do we need dev_is_pci()
> checks here?

Some platform devices may also call this.

> Can't this be done in the PCI probe path somehow, e.g.,
> in pci_set_bus_msi_domain() or something?

Yes, this can be done in pci_create_root_bus(). But it could only
handle the case that iommu drivers are initialed before PCI probing.

Regards,
Yongji