[ipxe-devel] iPXE with Virtualbox

[Andrew Bobulsky]

Hello Matthew, Michael,

Fine work on the bug hunting, Matthew!  Posts like yours are always
fun to read, particularly because I doubt I ever would have tracked
that down myself :)

Michael, I've been doing some research recently on x86 processor
modes, and while I couldn't begin to offer any solutions due to my
noobliness, some quick Google-Fu brought up these:
http://forums.devshed.com/embedded-programming-163/unreal-mode-issue-672039.html
*and* http://forum.sysinternals.com/topic21792_post115156.html

While the threads are approaching a year old and appear unresolved,
it's interesting that they're saying (I think) that access to expanded
memory seems to work fine /without/ first setting up the CPU registers
while PE=1.  Neat.  Obnoxious, but neat.

I guess the real question is if this is a VirtualBox bug, feature, or
both.  Praise the almighty Oracle ;)

Might it be possible to probe SMBIOS before attempting to set up the
CPU, and if VirtualBox is detected, skip that setup?  ...Not that I've
any clue if it would work, of course.  I've only been exploring x86
modes and peeking at assembly for a few weeks now :)

Best Regards,
Andrew Bobulsky


On Mon, Jan 24, 2011 at 9:18 AM, Matthew Walster <matthew at walster.org> wrote:
> On 24 January 2011 12:45, Michael Brown <mbrown at fensystems.co.uk> wrote:
>> Thanks for tracking this down, Matthew.  It's annoying that flat real mode
>> seems to cause problems in some hypervisors, even though it works on real
>> hardware.
>
> No problem at all - I had an hour spare and it was a good time to try
> "git bisect" out ;)
>
>> I can't just revert this change, since some later commits (e.g. "[romprefix]
>> Add .mrom format") depend upon it.  I'll rework it to use some form of
>> protected mode instead.
>
> I'm sorry to hear that. Please do let me know if there's any way I can
> be of assistance, even if it's just testing on a range of platforms.
>
> Matthew Walster
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