Re: [Xen-devel] progress and a problem

[Keir F. <Kei...@cl...>]

> On Sat, 26 Jun 2004, Keir Fraser wrote:
> 
> > Which stack are you talking about here? When Xen first deschedules
> > your while(1), the CPU should write CS,EIP,EFLAGS,SS,ESP onto Xen's
> > ring-0 stack.
> 
> ok, what interrupt does this? 

Any interrupt. Timer, disc, ... whatever happens to cause Xen to next
execute after you disable the mask. Xen always checks the pending and
mask flags on return to ring != 0.

> > When you get a callback, Xen should see that it is 'interrupting' an
> > existing ring-1 activation, and read the appropriate SS,ESP from its
> > own (ring-0) stack. When it writes the activation frame for teh
> > callback, it will only write CS,EIP,EFLAGS. SS,ESP will not be written
> > to your ring-1 stack because the IRET at the end of your callback
> > handler will not be changing privilege levels.
> 
> ok, I see your point. I'm really puzzled about this bad ss/sp pair. It 
> makes no sense.

I'll take a look at stack traces if you want to post me some suitably
annotated ones.

 -- Keir