On Sat, Mar 20, 2010 at 3:18 PM, Avi Kivity <address@hidden> wrote:
On 03/20/2010 10:55 AM, Alexander Graf wrote:
I'd say that a GSoC project would rather focus on making a guest
OS work
than working on generic big real mode. Having Windows 98 support
is way more
visible to the users. And hopefully more fun to implement too,
as it's a
visible goal :-).
Big real mode allows you to boot various OSes, such as that old
Ubuntu/SuSE boot loader which triggered the whole thing.
I thought legacy Windows uses it too?
IIRC even current Windows (last I checked was XP, but it's probably
true for
newer) invokes big real mode inadvertently. All it takes is not to
clear fs
and gs while switching to real mode. It works because the real
mode code
never uses gs and fs (i.e. while we are technically in big real
mode, the
guest never relies on this), and because there are enough hacks in
vmx.c to
make it work (restoring fs and gs after the switch back). IIRC
there are
other cases of invalid guest state that we hack into place during
mode
switches.
Either way - then we should make the goal of the project to
support those
old boot loaders. IMHO it should contain visibility. Doing
theoretical stuff
is just less fun for all parties. Or does that stuff work already?
Mostly those old guests aged beyond usefulness. They are still
broken, but
nobody installs new images. Old images installed via workarounds
work.
Goals for this task could include:
- get those older guests working
- get emulate_invalid_guest_state=1 to work on all supported guests
- switch to emulate_invalid_guest_state=1 as the default
- drop the code supporting emulate_invalid_guest_state=0 eventually
To this end I guess the next logical step is to compile a list of
guests that are currently not working/work with hacks only, and get
them working. Here are some suggestions:
- MINIX 3.1.6 (developers have been recently filing bug reports
because of boot failures)
- Win XP with emulation enabled
- FreeDOS with memory extenders
Any other guests you'd like to see on this list?