Re: adding support for above 2giga to kvm (include patchs)

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

On Tue, 2007-08-14 at 17:21 -0500, Ryan Harper wrote:
> * Ryan Harper <ryanh-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> [2007-08-14 15:44]:
> > * Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org> [2007-08-14 15:00]:
> > > i am sorry, i wrote you message and it get messed.
> > > 
> > > anyway you remember in the old patch the:
> > > +    if (ram_size > 0xf0000000)
> > > >      val = 640; /* base memory in K */
> > > i bet this is the problem :)
> > 
> > I removed that now and I didn't help =(
>  
> So, I don't think passing the structure as a pointer works.  The 16-bit
> compiler bcc has a number of quirks.  I don't pretend to understand what
> the issue is here, but, changing the signature of set_e820_range() to:

A pointer on the stack is not the same as a normal pointer in 16-bit
mode (one is relative to the stack segment and the other is relative to
data segment).

It may be that when Linux and Windows make calls into e820, ds == ss but
when memtest86 does, ds != ss.  I suspect this is why the BOCHS bios
code goes out of it's way to pass everything by value (and why there are
so many functions with a huge number of arguments).

I've had this issue myself with the SCSI boot ROM.

Regards,

Anthony Liguori

> void set_e820_range(ES, DI, start, end, extra_start, extra_end, type)
>      Bit16u ES;
>      Bit16u DI;
>      Bit32u start;
>      Bit32u end;
>      Bit16u extra_start;
>      Bit8u  extra_end;
>      Bit16u type;
> {
> 
> and the callers accordingly, fixes the issue with memtest iso.  I can
> still boot guests with more than 4G, and memtest sees the correct
> amount, above and below 4G.
> 


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