Re: i686 quirk for AMD Geode

Willy Tarreau
2009-11-12T05:40:17Z

On Wed, Nov 11, 2009 at 09:31:26PM -0800, H. Peter Anvin wrote:
> On 11/11/2009 09:27 PM, Willy Tarreau wrote:
> >
> > Right. However we just noticed that with the KVM emulator, you
> > can make it loop for a long time if you feed it with prefixes
> > only. For instance, write a function which does zillions of 0x66
> > (data size prefix) then return (0xC3) : 66 66 66 ... 66 C3.
> >
> > This is typically the sort of things we must be very careful about
> > in emulators, because we don't want users to steal large amounts
> > of system CPU time doing nothing.
> >
>
> That is a (serious) bug in the KVM interpreter, and indeed the exact
> kind of issues interpreters tend to have... which is why I'd like one
> piece of code with one set of bugs, and more eyeballs on that one piece
> of code so they can be fixed.

Well, I could try to work on a fix (basically the same principle as in
mine, with prefix flags), but I simply don't know how to test the code.
I've never experimented with KVM yet and learned it embeds an emulator
for the first time a few days ago in this thread :-/ If it's easy to
make use of it, I'm not opposed to try.

Willy