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From 72cc005ad139d9d5d4bf2cb7402cf730c6726fd3 Mon Sep 17 00:00:00 2001
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From: Cornelia Huck <cohuck@redhat.com>
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Date: Wed, 17 Apr 2019 13:57:37 +0100
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Subject: [PATCH 20/24] s390x/pci: Fix hotplugging of PCI bridges
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RH-Author: Cornelia Huck <cohuck@redhat.com>
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Message-id: <20190417135741.25297-21-cohuck@redhat.com>
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Patchwork-id: 85801
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O-Subject: [RHEL-8.1.0 qemu-kvm PATCH v2 20/24] s390x/pci: Fix hotplugging of PCI bridges
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Bugzilla: 1699070
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Jens Freimann <jfreimann@redhat.com>
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From: David Hildenbrand <david@redhat.com>
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When hotplugging a PCI bridge right now to the root port, we resolve
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pci_get_bus(pdev)->parent_dev, which results in a SEGFAULT. Hotplugging
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really only works right now when hotplugging to another bridge.
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Instead, we have to properly check if we are already at the root.
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Let's cleanup the code while at it a bit and factor out updating the
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subordinate bus number into a separate function. The check for
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"old_nr < nr" is right now not strictly necessary, but makes it more
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obvious what is actually going on.
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Most probably fixing up the topology is not our responsibility when
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hotplugging. The guest has to sort this out. But let's keep it for now
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and only fix current code to not crash.
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: David Hildenbrand <david@redhat.com>
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Message-Id: <20190130155733.32742-3-david@redhat.com>
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Reviewed-by: Collin Walling <walling@linux.ibm.com>
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Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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(cherry picked from commit 150f462538a6f3b78efe785c911669375032b0d2)
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Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/s390x/s390-pci-bus.c | 28 +++++++++++++++++++---------
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 1 file changed, 19 insertions(+), 9 deletions(-)
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diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
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index 309ad79..a0f7245 100644
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--- a/hw/s390x/s390-pci-bus.c
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+++ b/hw/s390x/s390-pci-bus.c
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@@ -881,6 +881,21 @@ static void s390_pcihost_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
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     }
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 }
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+static void s390_pci_update_subordinate(PCIDevice *dev, uint32_t nr)
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+{
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+    uint32_t old_nr;
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+
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+    pci_default_write_config(dev, PCI_SUBORDINATE_BUS, nr, 1);
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+    while (!pci_bus_is_root(pci_get_bus(dev))) {
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+        dev = pci_get_bus(dev)->parent_dev;
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+
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+        old_nr = pci_default_read_config(dev, PCI_SUBORDINATE_BUS, 1);
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+        if (old_nr < nr) {
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+            pci_default_write_config(dev, PCI_SUBORDINATE_BUS, nr, 1);
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+        }
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+    }
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+}
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+
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 static void s390_pcihost_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
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                               Error **errp)
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 {
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@@ -889,26 +904,21 @@ static void s390_pcihost_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
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     S390PCIBusDevice *pbdev = NULL;
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     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) {
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-        BusState *bus;
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         PCIBridge *pb = PCI_BRIDGE(dev);
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-        PCIDevice *pdev = PCI_DEVICE(dev);
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+        pdev = PCI_DEVICE(dev);
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         pci_bridge_map_irq(pb, dev->id, s390_pci_map_irq);
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         pci_setup_iommu(&pb->sec_bus, s390_pci_dma_iommu, s);
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-        bus = BUS(&pb->sec_bus);
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-        qbus_set_hotplug_handler(bus, DEVICE(s), errp);
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+        qbus_set_hotplug_handler(BUS(&pb->sec_bus), DEVICE(s), errp);
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         if (dev->hotplugged) {
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             pci_default_write_config(pdev, PCI_PRIMARY_BUS,
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                                      pci_dev_bus_num(pdev), 1);
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             s->bus_no += 1;
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             pci_default_write_config(pdev, PCI_SECONDARY_BUS, s->bus_no, 1);
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-            do {
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-                pdev = pci_get_bus(pdev)->parent_dev;
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-                pci_default_write_config(pdev, PCI_SUBORDINATE_BUS,
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-                                         s->bus_no, 1);
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-            } while (pci_get_bus(pdev) && pci_dev_bus_num(pdev));
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+
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+            s390_pci_update_subordinate(pdev, s->bus_no);
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         }
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     } else if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
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         pdev = PCI_DEVICE(dev);
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-- 
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1.8.3.1
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