Re: [PATCH] pl031: Expose RTCICR as proper WC register

[Peter Maydell]

On Tue, 12 Nov 2019 at 07:28, Alexander Graf <address@hidden> wrote:
>
> Hey Peter,
>
> On 08.11.19 17:58, Peter Maydell wrote:
> > Did you find this because you had a guest that assumed the
> > other behaviour? This bug has been in QEMU for a very long time,
> > and it seems odd for a guest to deliberately perform an action
> > (writing 0) which is documented to have no effect on the device...
>
> We found this bug by trying to find justification for the behavior in
> the spec and apparently my spec reading skills were lacking. I could not
> find the reference you cited above.
>
> So no, I did not see any guest breakage.
>
> I still think that being consistent with the actual PL031 spec is
> preferable though. If any real world guest breaks because of this, we
> can still revert this patch and document the exact breakage in the
> comment instead.

Yeah, I agree; I'm essentially just gathering material
for the commit message here. (The gold standard would be
to go find some hardware with a real pl031 and prod it
to confirm behaviour, but that's more effort than really
seems justified to me.)

thanks
-- PMM