[libvirt] [PATCH 1/3] qemu: Tweak auto adding PCI bridge controller when extending default PCI bus

[Erik Skultety]

In case we find out, there are more PCI devices to be connected
than there are available slots on the default PCI bus, we automatically add a
new bus and a related PCI bridge controller as well. As there are no free slots
left on the default PCI bus, PCI bridge controller gets a free slot on a
newly created PCI bus which causes qemu to refuse to start the guest.
This fix introduces a new function qemuDomainPCIBusFullyReserved which
is checked right before we possibly try to reserve a slot for PCI bridge
controller.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1132900
---
 src/qemu/qemu_command.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 3346e95..06def5f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1445,6 +1445,18 @@ qemuDomainSupportsPCI(virDomainDefPtr def)
     return false;
 }
 
+static bool
+qemuDomainPCIBusFullyReserved(virDomainPCIAddressBusPtr bus)
+{
+    size_t i;
+
+    for (i = bus->minSlot; i <= bus->maxSlot; i++)
+        if (!bus->slots[i])
+            return false;
+
+    return true;
+}
+
 int
 qemuDomainAssignPCIAddresses(virDomainDefPtr def,
                              virQEMUCapsPtr qemuCaps,
@@ -1479,9 +1491,15 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
                 goto cleanup;
             if (qemuAssignDevicePCISlots(def, qemuCaps, addrs) < 0)
                 goto cleanup;
-            /* Reserve 1 extra slot for a (potential) bridge */
-            if (virDomainPCIAddressReserveNextSlot(addrs, &info, flags) < 0)
-                goto cleanup;
+
+            for (i = 0; i < addrs->nbuses; i++) {
+                if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i])) {
+
+                    /* Reserve 1 extra slot for a (potential) bridge */
+                    if (virDomainPCIAddressReserveNextSlot(addrs, &info, flags) < 0)
+                        goto cleanup;
+                }
+            }
 
             for (i = 1; i < addrs->nbuses; i++) {
                 virDomainPCIAddressBusPtr bus = &addrs->buses[i];
-- 
1.9.3