On Mon, Jun 01, 2015 at 12:27:52PM +0100, Maciej W. Rozycki wrote:
> > > Can you please try this diagnostic patch and report the value of FCSR
> > > printed ("FCSR is:"), and also tell me if the exception has now gone too?
> > >
> > > I'll submit the final fix, properly annotated, if your testing confirms
> > > my diagnosis.
> >
> > That got it to boot again. I added CPU ID to the printk as well, and got some
> > odd output from one of the CPUs:
> >
> > # dmesg | grep FCSR
> > [ 0.000000] CPU0: FCSR is: 00000000
> > [ 0.319158] CPU1: FCSR is: 00000000
> > [ 0.364971] CPU2: FCSR is: ffffffffa8000000
> > [ 0.404854] CPU3: FCSR is: 00000000
>
> The value reported for CPU2 merely shows FCC[7,5,3] bits set, nothing
> really odd about that, the CPU may well have come out of reset like this.
> Neither of the values reported though actually corresponds to the symptom
> you saw, can you double-check you didn't make a typo in your modification
> to `printk'?
Maciej, I don't see why the code is so careful about not trampeling
over any bits that may be set on bootup. I think we should rather fully
initialize all the exception bits to zero to have the FPU in a known good
state.
Ralf
