Perform various checks on whether the mapping should be allowed, based on
PCIe ACS (Access Control Services) settings and the topology between the
two peers.
Signed-off-by: Will Davis <wdavis@xxxxxxxxxx>
---
arch/x86/kernel/pci-nommu.c | 96 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 96 insertions(+)
diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
index da15918..58f5296 100644
--- a/arch/x86/kernel/pci-nommu.c
+++ b/arch/x86/kernel/pci-nommu.c
@@ -38,6 +38,101 @@ static dma_addr_t nommu_map_page(struct device *dev, struct page *page,
return bus;
}
+static dma_peer_addr_t nommu_map_peer_resource(struct device *dev,
+ struct device *peer,
+ struct resource *res,
+ unsigned long offset,
+ size_t size,
+ enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ struct pci_dev *ppeer = to_pci_dev(peer);
+ struct pci_dev *rpdev, *rppeer, *common_upstream;
+ struct pci_host_bridge *dev_host_bridge;
+ struct pci_host_bridge *peer_host_bridge;
+ struct pci_bus_region region;
+ dma_peer_addr_t dma_address;
+ int pos;
+ u16 cap;
+
+ /*
+ * Disallow the peer-to-peer mapping if the devices do not share a host
+ * bridge.
+ */
+ dev_host_bridge = pci_find_host_bridge(pdev->bus);
+ peer_host_bridge = pci_find_host_bridge(ppeer->bus);
+ if (dev_host_bridge != peer_host_bridge)
+ return DMA_ERROR_CODE;
+
+ if (!pci_is_pcie(pdev))
+ goto out;
+
+ /*
+ * Access Control Services (ACS) Checks
+ *
+ * ACS has a capability bit for P2P Request Redirects, but
+ * unfortunately it doesn't tell us much about the real capabilities of
+ * the hardware.
+ */
+ rpdev = pdev->bus->self;
+ rppeer = ppeer->bus->self;
+
+ while ((rpdev) && (pci_is_pcie(rpdev)) &&
+ (pci_pcie_type(rpdev) != PCI_EXP_TYPE_ROOT_PORT))
+ rpdev = rpdev->bus->self;
+
+ while ((rppeer) && (pci_is_pcie(rppeer)) &&
+ (pci_pcie_type(rppeer) != PCI_EXP_TYPE_ROOT_PORT))
+ rppeer = rppeer->bus->self;
+
+ common_upstream = pci_find_common_upstream_dev(pdev, ppeer);
+
+ /* If ACS is not implemented, we have no idea about P2P support. */
+ pos = pci_find_ext_capability(rpdev, PCI_EXT_CAP_ID_ACS);
+ if (!pos)
+ goto out;
+
+ /*
+ * If the devices are under the same root port and have a common
+ * upstream device, allow if the root port is further upstream from the
+ * common upstream device and the common upstream device has Upstream
+ * Forwarding disabled, or if the root port is the common upstream
+ * device and ACS is not implemented.
+ */
+ pci_read_config_word(rpdev, pos + PCI_ACS_CAP, &cap);
+ if ((rpdev == rppeer && common_upstream) &&
+ (((common_upstream != rpdev) &&
+ !pci_acs_enabled(common_upstream, PCI_ACS_UF)) ||
+ ((common_upstream == rpdev) && ((cap & PCI_ACS_RR) == 0))))
+ goto out;
+
+ if (cap & PCI_ACS_RR) {
+ /* If ACS RR is implemented and enabled, allow the mapping */
+ if (pci_acs_enabled(rpdev, PCI_ACS_RR))
+ goto out;
+
+ /*
+ * If ACS RR is implemented and disabled, allow if the devices
+ * are under the same root port.
+ */
+ if (!pci_acs_enabled(rpdev, PCI_ACS_RR) && rpdev == rppeer)
+ goto out;
+ }
+
+ return DMA_ERROR_CODE;
+
+out:
+ pcibios_resource_to_bus(pdev->bus, ®ion, res);
+ dma_address = region.start + offset;
+ WARN_ON(size == 0);
+ if (!check_addr("map_peer_resource", dev, dma_address, size))
+ return DMA_ERROR_CODE;
+ flush_write_buffers();
+ return dma_address;
+}
+
+
/* Map a set of buffers described by scatterlist in streaming
* mode for DMA. This is the scatter-gather version of the
* above pci_map_single interface. Here the scatter gather list
@@ -93,6 +188,7 @@ struct dma_map_ops nommu_dma_ops = {
.free = dma_generic_free_coherent,
.map_sg = nommu_map_sg,
.map_page = nommu_map_page,
+ .map_peer_resource = nommu_map_peer_resource,
.sync_single_for_device = nommu_sync_single_for_device,
.sync_sg_for_device = nommu_sync_sg_for_device,
.is_phys = 1,
--
2.4.6
--
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