[Qemu-devel] [Bug 1747056] Re: FreeDOS / MS-Dos / Windows 3.11 cannot perform reboot with 'isapc' machine

[Daniel Berrange]

I bisected seabios and found this seabios change to be the cause of the
problem

commit b837e68d5a6c1a5945513f1995875445a1594c8a (refs/bisect/bad)
Author: Kevin O'Connor <address@hidden>
Date:   Mon Nov 9 15:00:19 2015 -0500

    resume: Make KVM soft reboot loop detection more flexible
    
    Move the check for soft reboot loops from resume.c to shadow.c and
    directly check for the case where the copy of the BIOS in flash
    appears to be a memory alias instead.  This prevents a hang if an
    external reboot request occurs during the BIOS memcpy.
    
    Signed-off-by: Kevin O'Connor <address@hidden>

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https://bugs.launchpad.net/bugs/1747056

Title:
  FreeDOS / MS-Dos / Windows 3.11 cannot perform reboot with 'isapc'
  machine

Status in QEMU:
  New

Bug description:
  I was installing MS-Dos 6.22 + Windows 3.11 in preparation for running
  Microsoft Bob, and noticed that when they try to perform a reboot,
  they just get stuck. The console cursor stays flashing on/off, but the
  DOS prompt no longer responds to input.

  It is fairly easy to reproduce, even FreeDOS is impacted - download
  the FreeDOS bootable CDROM image, then

  $ qemu-img create demo.img 100MB

  $ qemu-system-x86_64 -machine isapc -cdrom ~/Downloads/FD12CD.iso
  -hda demo.img  -monitor stdio

  Wait for the installer to startup, and then in the monitor console run

    sendkey ctrl-alt-delete

  It will fail to reboot

  Testing shows this is a regression from QEMU 2.8.0 onwards, and git
  bisect further narrowed it down to a SEABIOS update

  commit 6e99f5741ff1b408ea76e6caf2bd4f76df4060e9 (HEAD, tag: 
pull-seabios-20161027-2, tag: pull-seabios-20161027-1, refs/bisect/bad)
  Author: Gerd Hoffmann <address@hidden>
  Date:   Thu Oct 27 16:42:28 2016 +0200

      seabios: update to 1.10.0 release.

  Note that this seems particular to the "isapc" machine type - with the
  "pc" machine type, reboot still works

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