diff mbox series

[v2,1/6] s390x/pci: Fix primary bus number for PCI bridges

Message ID 20190130155733.32742-2-david@redhat.com
State New
Headers show
Series s390x/pci: remaining hot/un)plug patches | expand

Commit Message

David Hildenbrand Jan. 30, 2019, 3:57 p.m. UTC 
The primary bus number corresponds always to the bus number of the
bus the bridge is attached to.

Right now, if we have two bridges attached to the same bus (e.g. root
bus) this is however not the case. The first bridge will have primary
bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.

While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
Setting it temporarily to that value (as discussed e.g. in [1]), is
only relevant for a running system that probes the buses. The value is
effectively unused for us just doing a DFS.

Also add a comment why we have to reassign during every reset (which I
found to be surprising.

Please note that hotplugging of bridges is in general still broken, will
be fixed next.

[1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/s390x/s390-pci-bus.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Comments

Collin Walling Feb. 4, 2019, 10:58 p.m. UTC | #1 
On 1/30/19 10:57 AM, David Hildenbrand wrote:
> The primary bus number corresponds always to the bus number of the
> bus the bridge is attached to.
> 
> Right now, if we have two bridges attached to the same bus (e.g. root
> bus) this is however not the case. The first bridge will have primary
> bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
> 
> While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
> Setting it temporarily to that value (as discussed e.g. in [1]), is
> only relevant for a running system that probes the buses. The value is
> effectively unused for us just doing a DFS.
> 
> Also add a comment why we have to reassign during every reset (which I
> found to be surprising.
> 
> Please note that hotplugging of bridges is in general still broken, will
> be fixed next.
> 
> [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---

Reviewed-by: Collin Walling <walling@linux.ibm.com>
diff mbox series

Patch

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index f017c1ded0..b7c4613fde 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -862,7 +862,8 @@  static void s390_pcihost_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
         qbus_set_hotplug_handler(bus, DEVICE(s), errp);
 
         if (dev->hotplugged) {
-            pci_default_write_config(pdev, PCI_PRIMARY_BUS, s->bus_no, 1);
+            pci_default_write_config(pdev, PCI_PRIMARY_BUS,
+                                     pci_dev_bus_num(pdev), 1);
             s->bus_no += 1;
             pci_default_write_config(pdev, PCI_SECONDARY_BUS, s->bus_no, 1);
             do {
@@ -1016,8 +1017,6 @@  static void s390_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
                                       void *opaque)
 {
     S390pciState *s = opaque;
-    unsigned int primary = s->bus_no;
-    unsigned int subordinate = 0xff;
     PCIBus *sec_bus = NULL;
 
     if ((pci_default_read_config(pdev, PCI_HEADER_TYPE, 1) !=
@@ -1026,7 +1025,7 @@  static void s390_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
     }
 
     (s->bus_no)++;
-    pci_default_write_config(pdev, PCI_PRIMARY_BUS, primary, 1);
+    pci_default_write_config(pdev, PCI_PRIMARY_BUS, pci_dev_bus_num(pdev), 1);
     pci_default_write_config(pdev, PCI_SECONDARY_BUS, s->bus_no, 1);
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, s->bus_no, 1);
 
@@ -1035,7 +1034,7 @@  static void s390_pci_enumerate_bridge(PCIBus *bus, PCIDevice *pdev,
         return;
     }
 
-    pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, subordinate, 1);
+    /* Assign numbers to all child bridges. The last is the highest number. */
     pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
                         s390_pci_enumerate_bridge, s);
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, s->bus_no, 1);
@@ -1046,6 +1045,10 @@  static void s390_pcihost_reset(DeviceState *dev)
     S390pciState *s = S390_PCI_HOST_BRIDGE(dev);
     PCIBus *bus = s->parent_obj.bus;
 
+    /*
+     * When resetting a PCI bridge, the assigned numbers are set to 0. So
+     * on every system reset, we also have to reassign numbers.
+     */
     s->bus_no = 0;
     pci_for_each_device(bus, pci_bus_num(bus), s390_pci_enumerate_bridge, s);
 }