[Bug 1806114] Re: Reading sectors from floppy with BIOS INT 13h is broken

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to another 
system. For this we need to know which bugs are still valid and which could be 
closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state 
back to "New" within the next 60 days, otherwise this report will be marked as 
"Expired". Or mark it as "Fix Released" if the problem has been solved with a 
newer version of QEMU already. Thank you and sorry for the inconvenience.

** Changed in: qemu
       Status: New => Incomplete

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Title:
  Reading sectors from floppy with BIOS INT 13h is broken

Status in QEMU:
  Incomplete

Bug description:
  I'm developing a game bootable from a floppy disk, written in i386
  assembly. I found out it doesn't work on newer QEMU versions. I
  managed to isolate the issue and it seems that there's a problem with
  handling of BIOS interrupt 13h when it comes to reading disk sectors
  (AH=02).

  I've written a simple test in assembly. It simply accesses four
  different floppy disk sectors and prints out the strings they contain.
  The problem is, the two latter strings don't show up at all nor the
  BIOS interrupt returns an error (CF set). I've attached the code to
  this bug report. I use following commands to compile it and run:

  $ nasm disk-test.asm -o disk-test.bin
  $ qemu-system-i386 -boot a -fda disk-test.bin

  After running, the expected output is:

      I am a test string from boot sector
      C:H:S 0:0:2 - Hello
      C:H:S 0:0:3 - there!
      C:H:S 0:1:4 - In QEMU you can't
      C:H:S 1:0:5 - see these two lines! :(

  while the actual output is:

      I am a test string from boot sector
      C:H:S 0:0:2 - Hello
      C:H:S 0:0:3 - there!

  
  So far, I found this problem in the current QEMU version for Ubuntu 18.04 
(Debian 1:2.11+dfsg-1ubuntu7.8), as well as in the 3.1.0-rc3 and 2.12.1 
versions, available on the www.qemu.org website. Thus, the issue doesn't seem 
to be very recent.

  To be sure, I ran the program on my other machine with older QEMU
  version (Debian 2.0.0+dfsg-2ubuntu1.43) and on my RaspberryPi 2
  (Debian 1.1.2+dfsg-6+deb7u25) and everything works as expected there.
  It also works well in VirtualBox.

  I hope these information are useful to you, however, I feel like this
  bug may be more related to Seabios. If so, please let me know and I
  will report it somewhere else.

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