[Qemu-devel] [RFC PATCH] pci: Differentiate PCI Express bus

[Alex Williamson <alex.williamson@redhat.com>]

When creating capabilities devices need to know what kind of bus
they're on.  If we're on an express bus without a parent_dev, then
we're on the root complex and need to use integrated endpoints
rather than standard endpoints.  When we're on an express bus with
a parent_dev we need to negotiate link parameters so that the
endpoint doesn't claim it's running x16, 8GT/s while the root port
above it claims x1, 2.5GT/s capability.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

This feels a bit kludgy so I'm sending this out as an RFC looking for
suggestions.  I played a little with creating a PCIBusClass, putting
is_express on the class, and instantiating a TYPE_PCIE_BUS that uses
TYPE_PCI_BUS as it's parent, but that gets overly complicated and
means that any time we instantiate a bus we need to figure out whether
to use legacy or express.  Any better ideas?  Thanks,

Alex

 hw/ioh3420.c            |    2 ++
 hw/pci/pci_bus.h        |    2 ++
 hw/q35.c                |    1 +
 hw/xio3130_downstream.c |    2 ++
 hw/xio3130_upstream.c   |    2 ++
 5 files changed, 9 insertions(+)

diff --git a/hw/ioh3420.c b/hw/ioh3420.c
index 95bceb5..186a46f 100644
--- a/hw/ioh3420.c
+++ b/hw/ioh3420.c
@@ -102,6 +102,8 @@ static int ioh3420_initfn(PCIDevice *d)
         return rc;
     }
 
+    br->sec_bus->is_express = true;
+
     pcie_port_init_reg(d);
 
     rc = pci_bridge_ssvid_init(d, IOH_EP_SSVID_OFFSET,
diff --git a/hw/pci/pci_bus.h b/hw/pci/pci_bus.h
index aef559a..a325f46 100644
--- a/hw/pci/pci_bus.h
+++ b/hw/pci/pci_bus.h
@@ -34,6 +34,8 @@ struct PCIBus {
        Keep a count of the number of devices with raised IRQs.  */
     int nirq;
     int *irq_count;
+
+    bool is_express; /* PCI Express bus or Legacy bus? */
 };
 
 typedef struct PCIBridgeWindows PCIBridgeWindows;
diff --git a/hw/q35.c b/hw/q35.c
index efebc27..f5fdcb0 100644
--- a/hw/q35.c
+++ b/hw/q35.c
@@ -55,6 +55,7 @@ static int q35_host_init(SysBusDevice *dev)
     }
     b = pci_bus_new(&s->host.pci.busdev.qdev, "pcie.0",
                     s->mch.pci_address_space, s->mch.address_space_io, 0);
+    b->is_express = true;
     s->host.pci.bus = b;
     qdev_set_parent_bus(DEVICE(&s->mch), BUS(b));
     qdev_init_nofail(DEVICE(&s->mch));
diff --git a/hw/xio3130_downstream.c b/hw/xio3130_downstream.c
index 7f00bc8..600ec06 100644
--- a/hw/xio3130_downstream.c
+++ b/hw/xio3130_downstream.c
@@ -66,6 +66,8 @@ static int xio3130_downstream_initfn(PCIDevice *d)
         return rc;
     }
 
+    br->sec_bus->is_express = true;
+
     pcie_port_init_reg(d);
 
     rc = msi_init(d, XIO3130_MSI_OFFSET, XIO3130_MSI_NR_VECTOR,
diff --git a/hw/xio3130_upstream.c b/hw/xio3130_upstream.c
index 70b15d3..b6fea60 100644
--- a/hw/xio3130_upstream.c
+++ b/hw/xio3130_upstream.c
@@ -62,6 +62,8 @@ static int xio3130_upstream_initfn(PCIDevice *d)
         return rc;
     }
 
+    br->sec_bus->is_express = true;
+
     pcie_port_init_reg(d);
 
     rc = msi_init(d, XIO3130_MSI_OFFSET, XIO3130_MSI_NR_VECTOR,