Re: [Xen-devel] VT/ioemu: vga memory access?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 16 May 2006, at 17:20, Petersson, Mats wrote:

> > I think I found the bug.  It's actually in handle_mmio() ;)
> > The "case INSTR_MOVS" has code which deals with page
> > boundaries.  The code allways _adds_ the count (ecx) to
> > figure whenever the "repz movsb" crosses a page boundary or
> > not.  In case the direction flag is set this isn't correct,
> > it should subtract instead.  Subsequently it mis-calculates
> > count, making it _larger_ than it was because the copy
> > wouldn't have crossed a page boundary, leading to the
> > negative ecx value in the register dump ...
> I think you're right...
>
> I'll write some simple test code to check it out, and let you know...
Hmmm... wouldn't it be nice if we didn't have a bespoke, buggy & 
incomplete emulator for hvm mmio. ;-)
 -- Keir


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