[Qemu-devel] [PATCH v4 2/3] pcie: add check for ari capability of pcie devices

[arei.gonglei]

From: Gonglei <address@hidden>

In QEMU, ARI Forwarding is enabled default at emulation of PCIe
ports. ARI Forwarding enable setting at firmware/OS Control handoff.
If the bit is Set when a non-ARI Device is present, the non-ARI
Device can respond to Configuration Space accesses under what it
interprets as being different Device Numbers, and its Functions can
be aliased under multiple Device Numbers, generally leading to
undesired behavior.

So, for PCI devices attached in PCIe root ports or downstream pots,
we should assure that its slot is not non-zero. For PCIe devices, which
ARP capability is not enabled, we also should assure that its slot
is not non-zero.

Signed-off-by: Gonglei <address@hidden>
---
 hw/pci/pci.c          |  4 ++++
 hw/pci/pcie.c         | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/pci/pcie.h |  1 +
 3 files changed, 56 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 6ce75aa..22b7ca0 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1770,6 +1770,10 @@ static int pci_qdev_init(DeviceState *qdev)
         }
     }
 
+    if (pcie_cap_slot_check(bus, pci_dev)) {
+        return -1;
+    }
+
     /* rom loading */
     is_default_rom = false;
     if (pci_dev->romfile == NULL && pc->romfile != NULL) {
diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index 1babddf..b82211a 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -633,3 +633,54 @@ void pcie_ari_init(PCIDevice *dev, uint16_t offset, 
uint16_t nextfn)
                         offset, PCI_ARI_SIZEOF);
     pci_set_long(dev->config + offset + PCI_ARI_CAP, (nextfn & 0xff) << 8);
 }
+
+int pcie_cap_slot_check(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.
+         *
+         * In QEMU, ARI Forwarding is enabled default at emulation of PCIe
+         * ports. ARI Forwarding enable setting at firmware/OS Control handoff.
+         * If the bit is Set when a non-ARI Device is present, the non-ARI
+           Device can respond to Configuration Space accesses under what it
+         * interprets as being different Device Numbers, and its Functions can
+         * be aliased under multiple Device Numbers, generally leading to
+         * undesired behavior.
+         */
+        port_type = pcie_cap_get_type(pci_dev);
+        if (port_type == PCI_EXP_TYPE_DOWNSTREAM ||
+            port_type == PCI_EXP_TYPE_ROOT_PORT) {
+            if (!pci_is_express(dev) ||
+                (pci_is_express(dev) &&
+                !pcie_find_capability(dev, PCI_EXT_CAP_ID_ARI))) {
+                if (PCI_SLOT(dev->devfn) != 0) {
+                    error_report("PCIe: non-ARI device can't be populated"
+                                 " in slot %d", PCI_SLOT(dev->devfn));
+                    return -1;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
index d139d58..1d8f3f4 100644
--- a/include/hw/pci/pcie.h
+++ b/include/hw/pci/pcie.h
@@ -115,6 +115,7 @@ void pcie_add_capability(PCIDevice *dev,
                          uint16_t offset, uint16_t size);
 
 void pcie_ari_init(PCIDevice *dev, uint16_t offset, uint16_t nextfn);
+int pcie_cap_slot_check(PCIBus *bus, PCIDevice *dev);
 
 extern const VMStateDescription vmstate_pcie_device;
 
-- 
1.7.12.4