Hardware platforms usually describe the IOMMU topology using either device-tree pointers or vendor-specific ACPI tables. For virtual platforms that don't provide a device-tree, the virtio-iommu device contains a description of the endpoints it manages. That information allows us to probe endpoints after the IOMMU is probed (possibly as late as userspace modprobe), provided it is discovered early enough.
Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the endpoint is managed by a vIOMMU that will be loaded later, or 0 in any other case to avoid disturbing the normal DMA configuration methods. When CONFIG_VIRTIO_IOMMU_TOPOLOGY_HELPERS isn't selected, the call to virt_dma_configure() is compiled out. As long as the information is consistent, platforms can provide both a device-tree and a built-in topology, and the IOMMU infrastructure is able to deal with multiple DMA configuration methods. Acked-by: Bjorn Helgaas <bhelg...@google.com> Signed-off-by: Jean-Philippe Brucker <jean-phili...@linaro.org> --- drivers/pci/pci-driver.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 449466f71040..dbe9d33606b0 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -19,6 +19,7 @@ #include <linux/kexec.h> #include <linux/of_device.h> #include <linux/acpi.h> +#include <linux/virt_iommu.h> #include "pci.h" #include "pcie/portdrv.h" @@ -1605,6 +1606,10 @@ static int pci_dma_configure(struct device *dev) struct device *bridge; int ret = 0; + ret = virt_dma_configure(dev); + if (ret) + return ret; + bridge = pci_get_host_bridge_device(to_pci_dev(dev)); if (IS_ENABLED(CONFIG_OF) && bridge->parent && -- 2.28.0 _______________________________________________ iommu mailing list firstname.lastname@example.org https://lists.linuxfoundation.org/mailman/listinfo/iommu