grub is stuck in grub_biosdisk_check_int13_extensions() with qemu-kvm

[Alexander Lyakas]

Greetings everybody,

We are running qemu-kvm-0.14.0 on stock ubuntu-natty 2.6.38-8, and
booting stock ubuntu-precise image (3.2.0-25-generic), as a guest.
Occasionally, grub gets stuck before it reaches the OS selection menu.
After adding prints to grub, we discovered that it gets stuck in
grub_biosdisk_check_int13_extensions(), which does:

  struct grub_bios_int_registers regs;
  regs.edx = drive & 0xff;
  regs.eax = 0x4100;
  regs.ebx = 0x55aa;
  regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
  grub_bios_interrupt (0x13, &regs);

We have confirmed that drive=0x80 at this point.

Also, during normal boots we see that this function always returns the
same values: flags:0x3202 eax:0x3000 ebx:0xaa55 ecx:0x7. This is in
line with code in extboot.S: int13_handler() and
check_if_extensions_present().

Can anybody advise on how to debug this problem further?

I am also attaching a screenshot of a stuck grub.

Thanks,
Alex.

<<attachment: grub_hang_with_drive.png>>