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

From: Yongji Xie
Date: Wed May 25 2016 - 01:54:46 EST

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

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.