i8259: add -no-spurious-interrupt-hack option

This patch provides a way to optionally suppress spurious interrupts,
as a workaround for systems described below:

Some old operating systems do not handle spurious interrupts well,
and qemu tends to generate them significantly more often than
real hardware.

Examples:
  - Microport UNIX System V/386 v 2.1 (ca 1987)
    (The main problem I'm fixing: Without this patch, it panics
    sporadically when accessing the hard disk.)
  - AT&T UNIX System V/386 Release 4.0 Version 2.1a (ca 1991)
    See screenshot in "QEMU Official OS Support List":
    http://www.claunia.com/qemu/objectManager.php?sClass=application&iId=9
    (I don't have this system to test.)
  - A report about OS/2 boot lockup from 2004 by Hampa Hug:
    http://lists.nongnu.org/archive/html/qemu-devel/2004-09/msg00367.html
    (My patch was partially inspired by his.)
    Also: http://lists.nongnu.org/archive/html/qemu-devel/2005-06/msg00243.html
    (I don't have this system to test.)

Signed-off-by: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>
Signed-off-by: malc <av1474@comtv.ru>

1 files changed, 1 insertions, 0 deletions

diff --git a/sysemu.h b/sysemu.h
index 65552acee5..0170109e12 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -117,6 +117,7 @@ extern int graphic_depth;
 extern DisplayType display_type;
 extern const char *keyboard_layout;
 extern int win2k_install_hack;
+extern int no_spurious_interrupt_hack;
 extern int alt_grab;
 extern int ctrl_grab;
 extern int usb_enabled;