[PATCH v5 09/14] PCI: portdrv: Suppress kernel DMA ownership auto-claiming

[Lu Baolu]

If a switch lacks ACS P2P Request Redirect, a device below the switch can
bypass the IOMMU and DMA directly to other devices below the switch, so
all the downstream devices must be in the same IOMMU group as the switch
itself. The existing vfio framework allows the portdrv driver to be bound
to the bridge while its downstream devices are assigned to user space.
The pci_dma_configure() marks the iommu_group as containing only devices
with kernel drivers that manage DMA. Avoid this default behavior for the
portdrv driver in order for compatibility with the current vfio policy.

Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Suggested-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/pci/pcie/portdrv_pci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 35eca6277a96..2116f821c005 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -202,6 +202,8 @@ static struct pci_driver pcie_portdriver = {
 
 	.err_handler	= &pcie_portdrv_err_handler,
 
+	.no_kernel_api_dma = true,
+
 	.driver.pm	= PCIE_PORTDRV_PM_OPS,
 };
 
-- 
2.25.1