bootindex issue for virtio disks

Hello,

I have encountered a problem with the bootindex parameter for a KVM guest that has two virtio-blk disks.

host CPU: AMD Phenom II X4 955 Processor
host OS (first): x86_64 debian-squeeze (kernel 2.6.38 amd64) host OS (later): x86_64 debian-squeeze (kernel 3.0 amd64) guest OS (both disks): e.g. x86_64 debian-squeeze (2.6.32 amd64)

This is how I invoke qemu:

# /usr/bin/qemu-system-x86_64 \
  -m 256 \
  -name test4221 \
  -uuid f5dc124f-cbf4-6220-8b6b-15c0662be798 \
  -nodefconfig \
  -nodefaults \
  -drive file=/opt/dev/4223,if=none,id=mydrive0,format=raw \
  -device
virtio-blk-pci,bus=pci.0,addr=0x7,drive=mydrive0,id=mydisk0,bootindex=2 \
  -drive file=/opt/dev/4256,if=none,id=mydrive1,format=raw \
  -device
virtio-blk-pci,bus=pci.0,addr=0x4,drive=mydrive1,id=mydisk1,bootindex=1 \
  -vga cirrus

When both disks contain different OS images (Debian vs. Windows), everything is fine. But when I try two disks with the same OS on them, (no matter whether both are Windows or both are Debian), then when

first starting the VM (by a call to qemu-system-x86_64) or simply rebooting the VM again and again,

the disk that is booted from seems to be chosen rather randomly.

I had qemu-kvm 0.14.0 and seabios 0.6.2 on the host when the problem was first encountered. Then I removed both completely and did a "make install" with qemu-kvm 0.15 from the git repository.

# qemu-system-x86_64 -version
  QEMU emulator version 0.15.50 (qemu-kvm-devel), Copyright (c) \
  2003-2008 Fabrice Bellard

When I was still using seabios 0.6.2, I set its debug level to 5 and compared the debug output for the good and bad cases and found no difference.

Am I missing something or did I stumble over a bug?

Any hint would be welcome,

Elmar