[PATCH] MSR_RI not cleared early enough in entry.S

[Craig Chaney]

On Tue, Sep 28, 2004 at 03:44:05PM +1000, Paul Mackerras wrote:
> What exception do you think we might get?  Once we have successfully
> loaded r1 from the stack there should be no possibility of getting any
> exceptions until after the rfid, except for a machine check.  If we
> get a machine check in these circumstances we're toast but that should
> be extremely unlikely.
> 
> I think it is slightly more correct to clear RI before loading r1, but
> it won't make any difference to the actual outcome in any scenario
> that I can see.

You're right, the situation that I encountered this in was artificial.  I'm
working with an instruction tracing tool that records execution paths through
the kernel.  This tool looks for mtmsr instructions that clear MSR_RI; when
it finds one, it temporarily suspends single stepping.  I was getting a
single step exception after r1 was updated but before encountering the clear of
MSR_RI.

Thanks,
Craig