Re: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL

[Joakim Tjernlund <joakim.tjernlund@transmode.se>]

>
> On Fri, 2012-06-01 at 17:42 -0500, Scott Wood wrote:
> > On 06/01/2012 05:30 PM, Benjamin Herrenschmidt wrote:
> > > BTW. My point of view is that this whole business about MSR:DE is a HW
> > > design bug. There should be -no- (absolutely 0) interaction between the
> > > SW state and the HW debugger for normal operations unless the user of
> > > the debugger explicitly wants to change some state.
> >
> > I agree entirely, and e500mc at least has less of this than e500v2 (not
> > sure if it still needs MSR[DE], but supposedly it doesn't have the
> > requirement for there to be a valid instruction at the debug vector,
> > which is lots of fun when booting).  But this isn't exactly something
> > Freescale is going to replace existing chips over.
> >
> > Getting all the way to zero interaction would require a completely
> > separate debug facility so software can debug at the same time.  I'd be
> > all for that (and let's throw in a third, for the hypervisor), but I'm
> > not the one that needs to be convinced.
>
> You can find a good compromise. If you have some kind of SPR letting you
> know now many DACs and IACs are available, you could essentially
> "reserve" some for HW debug with the probe. Not as good as a fully
> separate facility but still better than stepping on each other toes.
>
> Things like DBCR should probably still be separated. There's no excuse
> for the MSR:DE bullshit tho :-)

hmm, where does this go w.r.t the patch? Got the feeling that the
best thing is to just turn MSR:DE on and be done with it?

 Jocke