[Qemu-devel] [PATCH v2 2/2] pci: add check for pcie root ports and downstream ports

[arei.gonglei]

From: Gonglei <address@hidden>

If ARI Forwarding is disabled, according to PCIe spec
section 7.3.1, only slot 0 with the device attached to
logic bus representing the link from downstream
ports and root ports.

So, adding check for PCIe downstream ports and root ports,
which avoid useless operation, both hotplug and coldplug.

Signed-off-by: Gonglei <address@hidden>
---
 hw/pci/pci.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index daeaeac..aa0af0c 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -773,6 +773,52 @@ static int pci_init_multifunction(PCIBus *bus, PCIDevice 
*dev)
     return 0;
 }
 
+static int pci_check_pcie_port(PCIBus *bus, PCIDevice *dev)
+{
+    Object *obj = OBJECT(bus);
+
+    if (pci_bus_is_root(bus)) {
+        return 0;
+    }
+
+    if (object_dynamic_cast(obj, TYPE_PCIE_BUS)) {
+        DeviceState *parent = qbus_get_parent(BUS(obj));
+        PCIDevice *pci_dev = PCI_DEVICE(parent);
+        uint8_t port_type;
+        /*
+         * Root ports and downstream ports of switches are the hot
+         * pluggable ports in a PCI Express hierarchy.
+         * PCI Express supports chip-to-chip interconnect, a PCIe link can
+         * only connect one pci device/Switch/EndPoint or PCI-bridge.
+         *
+         * 7.3. Configuration Transaction Rules (PCI Express specification 3.0)
+         * 7.3.1. Device Number
+         *
+         * Downstream Ports that do not have ARI Forwarding enabled must
+         * associate only Device 0 with the device attached to the Logical Bus
+         * representing the Link from the Port.
+         *
+         * If ARI Forwarding is not enabled on root ports and downstream
+         * ports, only support the devices with slot non-0, regardless of
+         * hotplug or coldplug.
+         */
+        port_type = pcie_cap_get_type(pci_dev);
+        if (port_type == PCI_EXP_TYPE_DOWNSTREAM ||
+            port_type == PCI_EXP_TYPE_ROOT_PORT) {
+            if (!pcie_cap_is_ari_enabled(pci_dev)) {
+                if (PCI_SLOT(dev->devfn) != 0) {
+                    error_report("PCIe: Port's ARI Forwarding is disabled, "
+                                 "device can't be populated in slot %d",
+                                 PCI_SLOT(dev->devfn));
+                    return -1;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
 static void pci_config_alloc(PCIDevice *pci_dev)
 {
     int config_size = pci_config_size(pci_dev);
@@ -827,6 +873,11 @@ static PCIDevice *do_pci_register_device(PCIDevice 
*pci_dev, PCIBus *bus,
 
     pci_dev->bus = bus;
     pci_dev->devfn = devfn;
+
+    if (pci_check_pcie_port(bus, pci_dev)) {
+        return NULL;
+    }
+
     dma_as = pci_device_iommu_address_space(pci_dev);
 
     memory_region_init_alias(&pci_dev->bus_master_enable_region,
-- 
1.7.12.4