Description of problem:
Boot a windows guest with 1 virtio serial bus and 30 serial ports, got BSOD.
Boot a RHEL6.1 guest with the same command line, guest can boot up successfully and work well.
Boot windows guset with 1 virtio serial bus and 29 serial ports, no problem

Version-Release number of selected component (if applicable):
virtio-win-prewhql-0.1-6
kernel-2.6.32-120.el6.x86_64
qemu-kvm-0.12.1.2-2.150.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Boot a windows guest with the 1 virtio serial bus and 30 serial ports. Command line:

/usr/libexec/qemu-kvm -m 4G -smp 4 -cpu cpu64-rhel6,+x2apic -usbdevice tablet -drive file=win2k8-64-serial/win2k8-64-serial.raw,format=raw,if=none,id=drive-ide0-0-0,werror=stop,rerror=stop,cache=none -device ide-drive,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,id=hostnet0,script=/etc/qemu-ifup0 -device virtio-net-pci,netdev=hostnet0,mac=00:10:20:3d:41:29,bus=pci.0,addr=0x4,id=net0 -boot c -uuid 36360dcb-c6a9-4708-ab68-78776b780ac8 -rtc-td-hack -no-kvm-pit-reinjection -monitor stdio -name win7-64 -vnc :10 -device virtio-serial-pci,id=virtio-serial0,max_ports=31,vectors=4,bus=pci.0 -chardev socket,id=channel0,path=/var/lib/libvirt/qemu/rhel6.channel0,server,nowait -device virtserialport,chardev=channel0,name=org.linux-kvm.port.0,bus=virtio-serial0.0,id=port0 -chardev socket,id=channel1,path=/var/lib/libvirt/qemu/rhel6.channel1,server,nowait -device virtserialport,chardev=channel1,name=org.linux-kvm.port.1,bus=virtio-serial0.0,id=port1 -chardev socket,id=channel2,path=/var/lib/libvirt/qemu/rhel6.channel2,server,nowait -device virtserialport,chardev=channel2,name=org.linux-kvm.port.2,bus=virtio-serial0.0,id=port2 -chardev socket,id=channel3,path=/var/lib/libvirt/qemu/rhel6.channel3,server,nowait -device virtserialport,chardev=channel3,name=org.linux-kvm.port.3,bus=virtio-serial0.0,id=port3 -chardev socket,id=channel4,path=/var/lib/libvirt/qemu/rhel6.channel4,server,nowait -device virtserialport,chardev=channel4,name=org.linux-kvm.port.4,bus=virtio-serial0.0,id=port4 -chardev socket,id=channel5,path=/var/lib/libvirt/qemu/rhel6.channel5,server,nowait -device virtserialport,chardev=channel5,name=org.linux-kvm.port.5,bus=virtio-serial0.0,id=port5 -chardev socket,id=channel6,path=/var/lib/libvirt/qemu/rhel6.channel6,server,nowait -device virtserialport,chardev=channel6,name=org.linux-kvm.port.6,bus=virtio-serial0.0,id=port6 -chardev socket,id=channel7,path=/var/lib/libvirt/qemu/rhel6.channel7,server,nowait -device virtserialport,chardev=channel7,name=org.linux-kvm.port.7,bus=virtio-serial0.0,id=port7 -chardev socket,id=channel8,path=/var/lib/libvirt/qemu/rhel6.channel8,server,nowait -device virtserialport,chardev=channel8,name=org.linux-kvm.port.8,bus=virtio-serial0.0,id=port8 -chardev socket,id=channel9,path=/var/lib/libvirt/qemu/rhel6.channel9,server,nowait -device virtserialport,chardev=channel9,name=org.linux-kvm.port.9,bus=virtio-serial0.0,id=port9 -chardev socket,id=channel10,path=/var/lib/libvirt/qemu/rhel6.channel10,server,nowait -device virtserialport,chardev=channel10,name=org.linux-kvm.port.10,bus=virtio-serial0.0,id=port10 -chardev socket,id=channel11,path=/var/lib/libvirt/qemu/rhel6.channel11,server,nowait -device virtserialport,chardev=channel11,name=org.linux-kvm.port.11,bus=virtio-serial0.0,id=port11 -chardev socket,id=channel12,path=/var/lib/libvirt/qemu/rhel6.channel12,server,nowait -device virtserialport,chardev=channel12,name=org.linux-kvm.port.12,bus=virtio-serial0.0,id=port12 -chardev socket,id=channel13,path=/var/lib/libvirt/qemu/rhel6.channel13,server,nowait -device virtserialport,chardev=channel13,name=org.linux-kvm.port.13,bus=virtio-serial0.0,id=port13 -chardev socket,id=channel14,path=/var/lib/libvirt/qemu/rhel6.channel14,server,nowait -device virtserialport,chardev=channel14,name=org.linux-kvm.port.14,bus=virtio-serial0.0,id=port14 -chardev socket,id=channel15,path=/var/lib/libvirt/qemu/rhel6.channel15,server,nowait -device virtserialport,chardev=channel15,name=org.linux-kvm.port.15,bus=virtio-serial0.0,id=port15 -chardev socket,id=channel16,path=/var/lib/libvirt/qemu/rhel6.channel16,server,nowait -device virtserialport,chardev=channel16,name=org.linux-kvm.port.16,bus=virtio-serial0.0,id=port16 -chardev socket,id=channel17,path=/var/lib/libvirt/qemu/rhel6.channel17,server,nowait -device virtserialport,chardev=channel17,name=org.linux-kvm.port.17,bus=virtio-serial0.0,id=port17 -chardev socket,id=channel18,path=/var/lib/libvirt/qemu/rhel6.channel18,server,nowait -device virtserialport,chardev=channel18,name=org.linux-kvm.port.18,bus=virtio-serial0.0,id=port18 -chardev socket,id=channel19,path=/var/lib/libvirt/qemu/rhel6.channel19,server,nowait -device virtserialport,chardev=channel19,name=org.linux-kvm.port.19,bus=virtio-serial0.0,id=port19 -chardev socket,id=channel20,path=/var/lib/libvirt/qemu/rhel6.channel20,server,nowait -device virtserialport,chardev=channel20,name=org.linux-kvm.port.20,bus=virtio-serial0.0,id=port20 -chardev socket,id=channel21,path=/var/lib/libvirt/qemu/rhel6.channel21,server,nowait -device virtserialport,chardev=channel21,name=org.linux-kvm.port.21,bus=virtio-serial0.0,id=port21 -chardev socket,id=channel22,path=/var/lib/libvirt/qemu/rhel6.channel22,server,nowait -device virtserialport,chardev=channel22,name=org.linux-kvm.port.22,bus=virtio-serial0.0,id=port22 -chardev socket,id=channel23,path=/var/lib/libvirt/qemu/rhel6.channel23,server,nowait -device virtserialport,chardev=channel23,name=org.linux-kvm.port.23,bus=virtio-serial0.0,id=port23 -chardev socket,id=channel24,path=/var/lib/libvirt/qemu/rhel6.channel24,server,nowait -device virtserialport,chardev=channel24,name=org.linux-kvm.port.24,bus=virtio-serial0.0,id=port24 -chardev socket,id=channel25,path=/var/lib/libvirt/qemu/rhel6.channel25,server,nowait -device virtserialport,chardev=channel25,name=org.linux-kvm.port.25,bus=virtio-serial0.0,id=port25 -chardev socket,id=channel26,path=/var/lib/libvirt/qemu/rhel6.channel26,server,nowait -device virtserialport,chardev=channel26,name=org.linux-kvm.port.26,bus=virtio-serial0.0,id=port26 -chardev socket,id=channel27,path=/var/lib/libvirt/qemu/rhel6.channel27,server,nowait -device virtserialport,chardev=channel27,name=org.linux-kvm.port.27,bus=virtio-serial0.0,id=port27 -chardev socket,id=channel28,path=/var/lib/libvirt/qemu/rhel6.channel28,server,nowait -device virtserialport,chardev=channel28,name=org.linux-kvm.port.28,bus=virtio-serial0.0,id=port28 -chardev socket,id=channel29,path=/var/lib/libvirt/qemu/rhel6.channel29,server,nowait -device virtserialport,chardev=channel29,name=org.linux-kvm.port.29,bus=virtio-serial0.0,id=port29
2.
3.
  
Actual results:
Guest got BSOD.

Expected results:
Guest can boot up successfully and work well.

Additional info: