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[Qemu-devel] [PATCH v1 2/2] s390x/pci: Fix hotplugging of PCI bridges


From: David Hildenbrand
Subject: [Qemu-devel] [PATCH v1 2/2] s390x/pci: Fix hotplugging of PCI bridges
Date: Tue, 22 Jan 2019 13:51:33 +0100

When hotplugging a PCI bridge right now to the root port, we resolve
pci_get_bus(pdev)->parent_dev, which results in a SEGFAULT. Hotplugging
really only works right now when hotplugging to another bridge.

Instead, we have to properly check if we are already at the root.

Let's cleanup the code while at it a bit and factor out updating the
subordiante bus number into a separate function. The check for
"old_nr < nr" is right now not strictly necessary, but makes it more
obvious what is actually going on.

Signed-off-by: David Hildenbrand <address@hidden>
---
 hw/s390x/s390-pci-bus.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index b7c4613fde..9b5c5fff60 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -843,6 +843,21 @@ static void s390_pcihost_pre_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
     }
 }
 
+static void s390_pci_update_subordinate(PCIDevice *dev, uint32_t nr)
+{
+    uint32_t old_nr;
+
+    pci_default_write_config(dev, PCI_SUBORDINATE_BUS, nr, 1);
+    while (!pci_bus_is_root(pci_get_bus(dev))) {
+        dev = pci_get_bus(dev)->parent_dev;
+
+        old_nr = pci_default_read_config(dev, PCI_SUBORDINATE_BUS, 1);
+        if (old_nr < nr) {
+            pci_default_write_config(dev, PCI_SUBORDINATE_BUS, nr, 1);
+        }
+    }
+}
+
 static void s390_pcihost_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
                               Error **errp)
 {
@@ -851,26 +866,21 @@ static void s390_pcihost_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
     S390PCIBusDevice *pbdev = NULL;
 
     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) {
-        BusState *bus;
         PCIBridge *pb = PCI_BRIDGE(dev);
-        PCIDevice *pdev = PCI_DEVICE(dev);
 
+        pdev = PCI_DEVICE(dev);
         pci_bridge_map_irq(pb, dev->id, s390_pci_map_irq);
         pci_setup_iommu(&pb->sec_bus, s390_pci_dma_iommu, s);
 
-        bus = BUS(&pb->sec_bus);
-        qbus_set_hotplug_handler(bus, DEVICE(s), errp);
+        qbus_set_hotplug_handler(BUS(&pb->sec_bus), DEVICE(s), errp);
 
         if (dev->hotplugged) {
             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 {
-                pdev = pci_get_bus(pdev)->parent_dev;
-                pci_default_write_config(pdev, PCI_SUBORDINATE_BUS,
-                                         s->bus_no, 1);
-            } while (pci_get_bus(pdev) && pci_dev_bus_num(pdev));
+
+            s390_pci_update_subordinate(pdev, s->bus_no);
         }
     } else if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
         pdev = PCI_DEVICE(dev);
-- 
2.17.2




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