[Qemu-devel] [Bug 1122492] [NEW] qemu and grub2 rescue floppy don't get along

[Cole Robinson]

Public bug reported:

With qemu.git as of Feb 11 2013:

# grub2-mkrescue -o test.img
# ./x86_64-softmmu/qemu-system-x86_64 -fda test.img -curses

SeaBIOS (version ?-20130206_051134-ccnode4)

iPXE v1.0.0-591-g7aee315
iPXE (http://ipxe.org) 00:03.0 C900 PCI2.10 PnP PMM+07FC7EC0+07F87EC0 C900


Booting from Hard Disk...
Boot failed: could not read the boot disk

Booting from Floppy...
GRUB loading....
Welcome to GRUB!

error: attempt to read or write outside of disk `fd0'.
Entering rescue mode...
grub rescue> 


Expected results: grub header and a normal usable grub prompt like 'grub>'


This was originally reported against qemu 0.15 in Fedora 16 at:

https://bugzilla.redhat.com/show_bug.cgi?id=784537

Some more info from that bug:

0) The images that grub2-mkrescue creates are odd mixtures of ISO images and 
disk images:
    file -r -k test.img
    test.img: # ISO 9660 CD-ROM filesystem data 'ISOIMAGE                       
 ' (bootable)
    - x86 boot sector; partition 1: ID=0xcd, active, starthead 0, startsector 
1, 4455 sectors, code offset 0x63 DOS executable (COM), boot code

1) The test image I use has a 2281472 byte size. If I append that with
zeroes to 2880 KB (2949120 bytes) then I get the expected results. So
there's a workaround. But I don't think it's an obvious workaround.

2) It's debatable whether this is a bug. If it's considered a bug, I'm
not sure whether qemu and/or grub2 is to blame. Should qemu (silently)
handle (floppy) disk image between 1440 KB and 2880 KB as if they
actually were 2880 KB in size? Or should grub2, if possible, zero pad
the images it creates to (in this case) a 2880 KB size?

3) Please note that there seems to be little one can do to leave "grub rescue" 
mode. Ie, "insmod normal" will fail too:
    grub rescue> insmod normal
    error: attempt to read or write outside of disk `fd0'.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1122492

Title:
  qemu and grub2 rescue floppy don't get along

Status in QEMU:
  New

Bug description:
  With qemu.git as of Feb 11 2013:

  # grub2-mkrescue -o test.img
  # ./x86_64-softmmu/qemu-system-x86_64 -fda test.img -curses

  SeaBIOS (version ?-20130206_051134-ccnode4)

  iPXE v1.0.0-591-g7aee315
  iPXE (http://ipxe.org) 00:03.0 C900 PCI2.10 PnP PMM+07FC7EC0+07F87EC0 C900

  
  Booting from Hard Disk...
  Boot failed: could not read the boot disk

  Booting from Floppy...
  GRUB loading....
  Welcome to GRUB!

  error: attempt to read or write outside of disk `fd0'.
  Entering rescue mode...
  grub rescue> 

  
  Expected results: grub header and a normal usable grub prompt like 'grub>'

  
  This was originally reported against qemu 0.15 in Fedora 16 at:

  https://bugzilla.redhat.com/show_bug.cgi?id=784537

  Some more info from that bug:

  0) The images that grub2-mkrescue creates are odd mixtures of ISO images and 
disk images:
      file -r -k test.img
      test.img: # ISO 9660 CD-ROM filesystem data 'ISOIMAGE                     
   ' (bootable)
      - x86 boot sector; partition 1: ID=0xcd, active, starthead 0, startsector 
1, 4455 sectors, code offset 0x63 DOS executable (COM), boot code

  1) The test image I use has a 2281472 byte size. If I append that with
  zeroes to 2880 KB (2949120 bytes) then I get the expected results. So
  there's a workaround. But I don't think it's an obvious workaround.

  2) It's debatable whether this is a bug. If it's considered a bug, I'm
  not sure whether qemu and/or grub2 is to blame. Should qemu (silently)
  handle (floppy) disk image between 1440 KB and 2880 KB as if they
  actually were 2880 KB in size? Or should grub2, if possible, zero pad
  the images it creates to (in this case) a 2880 KB size?

  3) Please note that there seems to be little one can do to leave "grub 
rescue" mode. Ie, "insmod normal" will fail too:
      grub rescue> insmod normal
      error: attempt to read or write outside of disk `fd0'.

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