diff options
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/pci/pci.c | 43 |
1 files changed, 40 insertions, 3 deletions
diff --git a/hw/pci/pci.c b/hw/pci/pci.c index c68498c0de..cbc7a32568 100644 --- a/hw/pci/pci.c +++ b/hw/pci/pci.c @@ -2646,12 +2646,49 @@ AddressSpace *pci_device_iommu_address_space(PCIDevice *dev) { PCIBus *bus = pci_get_bus(dev); PCIBus *iommu_bus = bus; + uint8_t devfn = dev->devfn; - while(iommu_bus && !iommu_bus->iommu_fn && iommu_bus->parent_dev) { - iommu_bus = pci_get_bus(iommu_bus->parent_dev); + while (iommu_bus && !iommu_bus->iommu_fn && iommu_bus->parent_dev) { + PCIBus *parent_bus = pci_get_bus(iommu_bus->parent_dev); + + /* + * The requester ID of the provided device may be aliased, as seen from + * the IOMMU, due to topology limitations. The IOMMU relies on a + * requester ID to provide a unique AddressSpace for devices, but + * conventional PCI buses pre-date such concepts. Instead, the PCIe- + * to-PCI bridge creates and accepts transactions on behalf of down- + * stream devices. When doing so, all downstream devices are masked + * (aliased) behind a single requester ID. The requester ID used + * depends on the format of the bridge devices. Proper PCIe-to-PCI + * bridges, with a PCIe capability indicating such, follow the + * guidelines of chapter 2.3 of the PCIe-to-PCI/X bridge specification, + * where the bridge uses the seconary bus as the bridge portion of the + * requester ID and devfn of 00.0. For other bridges, typically those + * found on the root complex such as the dmi-to-pci-bridge, we follow + * the convention of typical bare-metal hardware, which uses the + * requester ID of the bridge itself. There are device specific + * exceptions to these rules, but these are the defaults that the + * Linux kernel uses when determining DMA aliases itself and believed + * to be true for the bare metal equivalents of the devices emulated + * in QEMU. + */ + if (!pci_bus_is_express(iommu_bus)) { + PCIDevice *parent = iommu_bus->parent_dev; + + if (pci_is_express(parent) && + pcie_cap_get_type(parent) == PCI_EXP_TYPE_PCI_BRIDGE) { + devfn = PCI_DEVFN(0, 0); + bus = iommu_bus; + } else { + devfn = parent->devfn; + bus = parent_bus; + } + } + + iommu_bus = parent_bus; } if (iommu_bus && iommu_bus->iommu_fn) { - return iommu_bus->iommu_fn(bus, iommu_bus->iommu_opaque, dev->devfn); + return iommu_bus->iommu_fn(bus, iommu_bus->iommu_opaque, devfn); } return &address_space_memory; } |