Re: [RFC PATCH v3 0/3] Add segment limit checks to emulator

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On Sun, Jul 25, 2010 at 11:54:20AM +0300, Avi Kivity wrote:
>  On 07/24/2010 06:45 PM, Kevin O'Connor wrote:
> >On Mon, Jul 12, 2010 at 04:13:06PM +0300, Avi Kivity wrote:
> >>Does SeaBIOS use big real mode now?
> >SeaBIOS calls option roms in big real mode.  This is required by the
> >relevant specs.
> 
> Can you provide a pointer?

See the PMM spec section 2.2 and section 3.2.4.  (Sadly, I can't find
a link to the PMM spec on the web anymore - hopefully you have a
copy.)  Also see the PCI Firmware Specification v3.0 - section
5.2.1.9.

The specs don't require any code addresses to be >64K, but it does
require data access over 64K.  I doubt there are many systems that use
a code address >64K, because an interrupt in big real mode still only
stores a 16bit return address - thus an irq (or nmi) in that mode will
basically cause a crash.

-Kevin
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