Description of problem:
I've attached around 15 NICs to the machine via virt-manager.

Version-Release number of selected component:
qemu-system-x86-1.6.2-8.fc20

Additional info:
reporter:       libreport-2.2.3
backtrace_rating: 4
cmdline:        /usr/bin/qemu-system-x86_64 -machine accel=kvm -name centos7-2 -S -machine pc-i440fx-1.6,accel=kvm,usb=off -cpu Haswell -m 2048 -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 -uuid 4b8f6721-f561-4e4e-95bd-21bdc5c519b0 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/centos7-2.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -device pci-bridge,chassis_nr=1,id=pci.1,bus=pci.0,addr=0x1f -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1f -device pci-bridge,chassis_nr=3,id=pci.3,bus=pci.2,addr=0x1f -device pci-bridge,chassis_nr=4,id=pci.4,bus=pci.3,addr=0x1f -device pci-bridge,chassis_nr=5,id=pci.5,bus=pci.4,addr=0x1f -device pci-bridge,chassis_nr=6,id=pci.6,bus=pci.5,addr=0x1f -device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x5.0x7 -device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x5 -device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x5.0x1 -device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x5.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.3,addr=0x14 -drive file=/var/lib/libvirt/images/rhel7-clone.qcow2,if=none,id=drive-virtio-disk0,format=qcow2 -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive if=none,id=drive-ide0-0-0,readonly=on,format=raw -device ide-cd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:e7:97:10,bus=pci.0,addr=0x1e -netdev tap,fd=25,id=hostnet1,vhost=on,vhostfd=28 -device virtio-net-pci,netdev=hostnet1,id=net1,mac=52:54:00:9c:2e:2c,bus=pci.0,addr=0x1d -netdev tap,fd=29,id=hostnet2,vhost=on,vhostfd=30 -device virtio-net-pci,netdev=hostnet2,id=net2,mac=52:54:00:af:06:6b,bus=pci.0,addr=0x1c -netdev tap,fd=31,id=hostnet3,vhost=on,vhostfd=32 -device virtio-net-pci,netdev=hostnet3,id=net3,mac=52:54:00:02:09:97,bus=pci.0,addr=0x1b -netdev tap,fd=33,id=hostnet4,vhost=on,vhostfd=34 -device virtio-net-pci,netdev=hostnet4,id=net4,mac=52:54:00:38:5d:cc,bus=pci.0,addr=0x1a -netdev tap,fd=35,id=hostnet5,vhost=on,vhostfd=36 -device virtio-net-pci,netdev=hostnet5,id=net5,mac=52:54:00:72:cf:ed,bus=pci.0,addr=0x19 -netdev tap,fd=37,id=hostnet6,vhost=on,vhostfd=38 -device virtio-net-pci,netdev=hostnet6,id=net6,mac=52:54:00:05:d1:de,bus=pci.0,addr=0x18 -netdev tap,fd=39,id=hostnet7,vhost=on,vhostfd=40 -device virtio-net-pci,netdev=hostnet7,id=net7,mac=52:54:00:1d:65:ff,bus=pci.0,addr=0x17 -netdev tap,fd=41,id=hostnet8,vhost=on,vhostfd=42 -device virtio-net-pci,netdev=hostnet8,id=net8,mac=52:54:00:69:aa:e9,bus=pci.0,addr=0x16 -netdev tap,fd=43,id=hostnet9,vhost=on,vhostfd=44 -device virtio-net-pci,netdev=hostnet9,id=net9,mac=52:54:00:1b:dd:fb,bus=pci.0,a0,mac=52:54:00:57:be:d2,bus=pci.0,addr=0x14 -netdev tap,fd=47,id=hostnet11,vhost=on,vhostfd=48 -device virtio-net-pci,netdev=hostnet11,id=net11,mac=52:54:00:a3:b3:c5,bus=pci.0,addr=0x13 -netdev tap,fd=49,id=hostnet12,vhost=on,vhostfd=50 -device virtio-net-pci,netdev=hostnet12,id=net12,mac=52:54:00:d6:91:ad,bus=pci.0,addr=0x12 -netdev tap,fd=51,id=hostnet13,vhost=on,vhostfd=52 -device virtio-net-pci,netdev=hostnet13,id=net13,mac=52:54:00:39:ef:92,bus=pci.0,addr=0x11 -netdev tap,fd=53,id=hostnet14,vhost=on,vhostfd=54 -device virtio-net-pci,netdev=hostnet14,id=net14,mac=52:54:00:0d:69:ba,bus=pci.0,addr=0x10 -netdev tap,fd=55,id=hostnet15,vhost=on,vhostfd=56 -device virtio-net-pci,netdev=hostnet15,id=net15,mac=52:54:00:a9:fe:70,bus=pci.0,addr=0xf -netdev tap,fd=57,id=hostnet16,vhost=on,vhostfd=58 -device virtio-net-pci,netdev=hostnet16,id=net16,mac=52:54:00:7e:4e:69,bus=pci.0,addr=0xe -netdev tap,fd=59,id=hostnet17,vhost=on,vhostfd=60 -device virtio-net-pci,netdev=hostnet17,id=net17,mac=52:54:00:2f:56:c6,bus=pci.
crash_function: phys_section_add
executable:     /usr/bin/qemu-system-x86_64
kernel:         3.15.10-201.fc20.x86_64
runlevel:       N 5
type:           CCpp
uid:            107

Truncated backtrace:
Thread no. 1 (10 frames)
 #4 phys_section_add at /usr/src/debug/qemu-1.6.2/exec.c:775
 #5 register_subpage at /usr/src/debug/qemu-1.6.2/exec.c:835
 #6 mem_add at /usr/src/debug/qemu-1.6.2/exec.c:863
 #7 address_space_update_topology_pass at /usr/src/debug/qemu-1.6.2/memory.c:735
 #8 address_space_update_topology at /usr/src/debug/qemu-1.6.2/memory.c:764
 #9 memory_region_transaction_commit at /usr/src/debug/qemu-1.6.2/memory.c:799
 #10 pci_default_write_config at hw/pci/pci.c:1173
 #11 access_with_adjusted_size at /usr/src/debug/qemu-1.6.2/memory.c:477
 #12 memory_region_dispatch_write at /usr/src/debug/qemu-1.6.2/memory.c:989
 #13 io_mem_write at /usr/src/debug/qemu-1.6.2/memory.c:1748